Skeneimorph species (Gastropoda) from the Rockall and

47

Miscellanea Malacologica 4(4): 47-61, 31.X.2010

Skeneimorph species (Gastropoda) from the Rockall and Hatton Banks,

northeastern Atlantic Ocean

L. HOFFMAN1, B. Van HEUGTEN

2 & M. S. S. LAVALEYE

3

1Zoetermeer, the Netherlands ([email protected]), 2Oosterhout, the Netherlands ([email protected]), 3NIOZ, Texel, the Netherlands ([email protected])

ABSTRACT

A record is given on the occurrence and abundance of skeneimorph species in the families Trochaclididae, Pendromidae and

Turbinidae (including those species formerly placed in Skeneidae) that have been collected during the NIOZ expeditions to

the Rockall and Hatton Banks (2004-2008). A description is provided for two new species: Mikro hattonensis, and

Xyloskenea xenos (Skeneinae, Turbinidae, Gastropoda). Their holotypes have been deposited in the Zoological Museum

Amsterdam (University of Amsterdam). Two poorly known species have been figured and re-described: Granigyra tenera

(Jeffreys, 1883), and Ganesa nitidiuscula Jeffreys, 1883.

Key words: Northeastern Atlantic Ocean, Rockall Bank, Hatton Bank, Turbinidae, Skeneidae, Skenea, Ganesa, Mikro,

Xyloskenea, Granigyra, taxonomy, new species, HERMES, Moundforce.

INTRODUCTION

The Rockall and Hatton Banks are sea bottom

highs that have developed over Jurassic fault

blocks. These fault blocks were formed during

early failed continental rifts in the Early

Cretaceous. The failed rift systems are

preceding the successful rift that has developed

since the Cretaceous between the Western

European continent and the East Greenland

coastline in the North East Atlantic. The deep

Rockall Trough separates the Rockall Bank

from Ireland and Scotland. The Hatton Bank is

the NW extent of the larger Rockall and Hatton

Bank area. The Rockall Bank has a miniscule

island as a tip of a fault block in the North of

the structure.

The Hatton Bank is fully submerged. It

may be assumed that the sea bottom

environment in the Rockall-Hatton area has

been in a stable state for at least 65 million

years, i.e. the end of the Cretaceous. These

stable and isolated environments are known to

develop endemic species. The highs of the

present day banks form a conglomerate of

cold-water coral reefs. A rich fauna

community populates these highs of which the

most prominent groups are Mollusca, corals

and sponges.

Typical water depths where these

communities thrive are 500-700 m on the

Rockall Bank to 600-1100 m on the Hatton

Bank. The Royal Netherlands Institute for Sea

Research (NIOZ) has conducted detailed

studies on the faunal communities of cold-

water corals in the NE Atlantic Ocean.

MATERIAL AND METHODS

During expeditions conducted in 2004 (Mienis

et al., 2004 [Moundforce]), 2005 (van Duyl et

al., 2005 [HERMES]) and 2006 (Duineveld et

al., 2006 [HERMES]), box core samples have

been taken from the coral-rich sea-bottom in

the southeastern slope of the Rockall Bank and

in 2008 (Lavaleye et al., 2008 [HERMES]) on

the Hatton Bank.

Whereas some of these box cores have

been preserved and retained for other

investigations, other box core samples have

been investigated for their malacofauna.

Unfortunately, the great majority of these

samples only contained empty shells and,

hence, no material has been available for

anatomical studies.

Bottom samples from box cores have

been washed thoroughly with fresh water,

dried and sieved in fractions of 10 mm, 3 mm,

1 mm, 0.5 mm. Fractions larger than 10 mm

and 3 mm contained mostly large coral

fragments and few larger Mollusca; these have

been hand picked. Fractions of 1-3 mm have

been fully sorted under a microscope. The

fractions of 0.5-1 mm have been sampled and a

small volume has been fully sorted. The

remaining material has been enriched in a

counter-current washing process and the

enriched fraction has been fully sorted. The

smallest fraction has been fully enriched by

counter-current washing and representative

samples have been sorted. Taxonomy of the

specimen has been largely based on the online

CLEMAM database for European Mollusca.

48

Hoffman, Van Heugten & Lavaleye, 2010: Skeneimorph species

For all box core stations, statistical shell counts

have been carried out such that species

abundance by weight or sea-bottom area could

be estimated.

We have used as abundance unit

shells/kg-dry-sediment-weight and it must be

realised that its large uncertainty is caused by

inaccuracies introduced by sampling (location

and depth of penetration) as well as in the

information gathering (subjective hand sorting,

visual counts, statistical extrapolations,

subjective taxonomic classification). Typical

dry-weight sediment samples in the box cores

contain 0.3-20 kg. For large sample sets with

high-related abundance it is not meaningful to

specify the exact number of shells as this has

often been based on statistical extrapolation of

sub-samples. For rare species, frequently the

fully sorted shell set has been investigated but

then the abundance is meaningless with only

few specimens available and it has been

omitted consequently.

Representatives of most species have

been digitally photographed using a

stereomicroscope camera and a computer.

Images have been taken as spherical slices at

regular focusing distances and the set of

images have been synthetically combined into

one sharp image using Helicon Focus software.

Alternatively, rare specimens have been

selected for SEM photography; they have been

cleaned in a weak bleach solution, rinsed in

fresh water, subjected to ultrasonic cleaning.

Subsequently, they have been mounted for

SEM photography.

The class of Archaeogastropoda and in

particular the subfamily Skeneinae in the

family Turbinidae is predominantly

represented in the malacofauna, both in terms

of number of specimens as well in the number

of species. In 2008, Hoffman et al. discussed

four new skeneid species in the new genus

Lopheliella from the Rockall Bank.

The holotypes of the genera

Lopheliella, Mikro and Xyloskenea are in the

collection of the Zoological Museum

Amsterdam (formally part of University of

Amsterdam). All remaining material is either

in the collection of the National Museum of

Natural History ‘Naturalis’ in Leiden, the

Netherlands or in the collections of the authors.

In this paper, we add two more new

species in Skeneinae. Their holotypes have

been deposited in the Zoological Museum

Amsterdam. A few paratypes have been

retained in the collections of the authors.

ABBREVIATIONS

CLEMAM = Check-List of European Marine

Mollusca

HERMES = Hotspot Ecosystem Research of the

Margins of European Seas

n. sp. = new species

NIOZ = Royal Netherlands Institute for Sea

Research, Texel

ZMA = Zoological Museum Amsterdam

ACKNOWLEDGEMENTS

The authors express their appreciation to NIOZ

for allowing to work the unique material and to

publish the results of these studies. We greatly

acknowledge the assistance of captain, crew,

technicians and scientists on board of RV

‘Pelagia’ during the cruises.

We particularly thank Robert G.

Moolenbeek (ZMA) for stimulating

discussions, his knowledgeable advice on the

taxonomy and the provision of literature. He

has been most cooperative in allowing the first

author to use the SEM facility at the University

of Amsterdam for micro-photographic

pictures. Bram van der Bijl, Marien J. Faber

and an anonymous referee critically read the

manuscript.

SYSTEMATICS

Family: Trochaclididae

Trochaclis islandicus Warén, 1989

Trochaclis islandicus Warén, 1989: 9-11, figs 6-7

Material examined.- ROCKALL BANK: Moundforce 2004/29, depth 1443 m,

1 shell; Hermes 2006/12, depth 1091 m, 3 shells;

HATTON BANK: Hermes 2008/36, depth 700 m, 9

shells; Hermes 2008/117, depth 958 m, 12 shells.

49

Miscellanea Malacologica 4(4): 47-61

Family: Pendromiidae

Rugulina fragilis (G.O. Sars, 1878)

(Figs 1-3)

Adeorbis fragilis G.O. Sars, 1878: 213, tab. 22, figs 19a-c

Rugulina fragilis: Warén, 1991: 71-73, figs 11A-E, 13A-

B

Material examined.- ROCKALL BANK: Moundforce 2004/37, depth 557 m;

Hermes 2005/15, depth 593 m; Hermes 2005/34, depth

767 m; Hermes 2006/10C, depth 587 m; Hermes

2006/12, 1091 m; Hermes 2006/23A, depth 578 m;


1087 m; HATTON BANK: Hermes 2008/35, depth 796

m; Hermes 2008/36, depth 700 m; Hermes 2008/59,

depth 788 m; Hermes 2008/92, depth 822 m. Abundances

are 6.5 shells/kg at 400-600 m, 6.9 shells/kg at 600-800

m, 2.7 shells/kg at 1000-1200 m.

Rugulina species

(Figs 4-6)

Material examined.- HATTON BANK: Hermes 2008, St.117, depth 958 m, 1

fragmentary shell.

Description.-

Fragile well rounded tonnoid-shaped shell,

height 2.3 mm, width 2.3 mm, with radial

regular rib structure. Protoconch is eroded and

hence unknown. Teleoconch whorls are well

rounded but somewhat oval in cross-section.

The base of the outline is a well-rounded base.

The outer lip is sharp. The suture is shallow.

Umbilicus is open and deep. The aperture is

prosocline. Sharp radial ribs dominate the

surface texture: about 21 on the body whorl.

Fine prosocline growth lines are evident. The

umbilical area is rather smooth. The single

shell is somewhat translucent cream white.

Discussion.-

The specimen has been placed in Rugulina in

the family Pendromiidae because of its

superficial resemblance to R. fragilis. Once

more complete specimen and/or soft parts are

available, a more conclusive taxonomic

placement can be made.

Family: Turbinidae

Skenea areolata (G.O. Sars, 1878)

Cyclostrema areolatum G.O. Sars, 1878: 345, tab. 34,

figs 6a-d

Skenea areolata: Warén, 1991: 58, figs 3A-C


Moundforce 2004/41C, depth 784 m; Hermes 2005/15,

depth 593 m; Hermes 2005/34, depth 767 m; Hermes

2006/10C, depth 578 m; Hermes 2006/12, depth 1091 m;

Hermes 2006/23A, depth 578 m; Hermes 2006/56, depth

578 m; Hermes 2006/65, depth 1087 m; HATTON

BANK: Hermes 2008/36, depth 700 m; Hermes 2008/92,

depth 822 m; Hermes 2008/117, depth 958 m.

Abundances are 72.2 shells/kg at 400-600 m, 11.8

shells/kg at 600-800 m, 2.2 shells/kg at 1000-1200 m, 2.4

shells/kg at 1443 m.

Skenea basistriata (Jeffreys, 1877)

Cyclostrema basistriata Jeffreys, 1877: 234

Skenea basistriata: Graham, 1988: 138, fig. 47

Skenea basistriata: Warén, 1993: 176, figs 16A-F, 17A-D

Material examined.- ROCKALL BANK: Hermes 2006/12, depth 1091 m;

Hermes 2006/65, depth 1087 m.

Skenea larseni Warén, 1993

Skenea larseni Warén, 1993: 173, figs 11D-F, 12A, 12C,

12E, 13C, 14A-B, 15C-D

Material examined.- ROCKALL BANK: Moundforce 2004/41C, depth 784








2008/117, depth 958 m. Abundances are 22 shells/kg at

400-600 m and 13 shells/kg at 1000-1200 m.

Skenea ossiansarsi Warén, 1991

Skenea ossiansarsi Warén, 1991: 58-60, figs 4C-D, 6F,

9C-D









2008/92, depth 822 m; Hermes 2008/117, depth 958 m.

Abundances are 453 shells/kg at 400-600 m and 703

shells/kg at 600-800 m, 118 shells/kg at 1000-1200 m.

50


Skenea peterseni (Friele, 1877)

Cyclostrema peterseni Friele, 1877: 3

Skenea peterseni: Warén, 1991: 60-61, figs 3F, 4A-B, 6D

Skenea peterseni: Warén, 1993: 175, figs 11A-C, 12B,

12D, 13B, 15A-B



1087 m.

Skenea polita Warén, 1993

Skenea polita Warén, 1993: 171-173, figs 10A-E, 13A


1 old shell.

Skenea profunda (Friele, 1879)

Cyclostrema profundum Friele, 1879: 272

Skenea profunda: Warén, 1991: 65, figs 5C, 7B



Skenea rugulosa (G.O. Sars, 1878)

Cyclostrema rugulosum G.O. Sars, 1878: 129, tab. 21,

figs a-d

Skenea rugulosa: Warén, 1991: 63-64, figs 3E, 4E-F, 6C,

9F


Hermes 2005/34, depth 767 m; Hermes 2006/10C, depth

578 m; Hermes 2006/12, depth 1091 m; Hermes 2006/56,

depth 578 m; Hermes 2006/65, depth 1087 m; HATTON


depth 700 m; Hermes 2008/59, 788 m; Hermes 2008/92,

depth 822 m; Hermes 2008/117, depth 958 m.

Abundances are 120 shells/kg at 400-600 m and 16

shells/kg at 600-800 m, 118 shells/kg at 1000-1200 m and

37 shells/kg at 1443 m.

Skenea trochoides (Friele, 1876)

Cyclostrema trochoides Jeffreys MS - Friele, 1876: 60

Skenea trochoides: Warén, 1991: 58, figs 2E-F, 3D, 3G,

6E, 8B




BANK: Hermes 2008/36, depth 700 m; Hermes

2008/117, depth 958 m.

Skenea turgida (Odhner, 1912)

Cyclostrema turgidum Odhner, 1912: 79

Skenea turgida: Warén, 1991: 65, figs 5D, 5G, 7D, 9A



1087 m.

Lopheliella hermesae Hoffman, van Heugten & Lavaleye, 2008

Lopheliella hermesae Hoffman et al., 2008: 43, figs 16-

19, 23

Material examined.- ROCKALL BANK: Hermes 2005/34, depth 767 m,

holotype, 1 shell; Hermes 2005/15, depth 593 m, 1 shell;

Hermes 2005/23, depth 667 m, 1 shell; Hermes 2006/56,

depth 578 m, 1 shell.

Lopheliella moolenbeeki Hoffman, van Heugten & Lavaleye, 2008

Lopheliella moolenbeeki Hoffman et al., 2008: 41-42,

figs 6-9, 21

Material examined.- ROCKALL BANK: Hermes 2006/56, holotype, depth

578 m, >200 paratypes; Moundforce 2004/37, depth 557

m, >200 shells; Hermes 2005/15, depth 593 m, 16 shells;

Hermes 2005/23, depth 667 m, > 20 shells; Hermes

2005/34, depth 767 m, 4 shells; Hermes 2006/10C, depth

587 m, 36 shells. HATTON BANK: Hermes 2008/117,

depth 958 m, 1 shell.

Lopheliella moundforceae Hoffman, van Heugten & Lavaleye, 2008

Lopheliella moundforceae Hoffman et al., 2008: 42-43,

figs 10-15, 22

Material examined.- ROCKALL BANK: Hermes 2006/28A, depth 588 m,

holotype, 1 shell; Moundforce 2004/37, depth 557 m, 2

worn shells; Moundforce 2004/41C, depth 784 m, 6 worn

shells; Hermes 2005/23, depth 667 m, 4 shells; Hermes

2006/10C, depth 578 m, 6 worn shells.

Lopheliella rockallensis Hoffman, van Heugten & Lavaleye, 2008

51


Lopheliella rockallensis Hoffman et al., 2008: 41, figs 1-

5, 20

Material examined.- ROCKALL BANK: Hermes 2006/St.56, holotype, depth

578 m, >100 paratypes; Moundforce 2004/37, depth 557

m, 30 shells; Hermes 2005/15, depth 593 m, 13 shells;

Hermes 2005/23, depth 667 m, >20 shells; Hermes

2005/34, depth 767 m, 11 shells; Hermes 2006/10C,

depth 587 m, 7 shells; Hermes 2006/23A, depth 587 m, 2

shells.

Cirsonella gaudryi (Dautzenberg and Fischer, 1896)

Tharsis gaudryi Dautzenberg & Fischer H., 1896: 486,

plate 21 figs 13-15

Material examined.- HATTON BANK: Hermes 2008/117, 958 m.

Cirsonella romettensis (Granata-Grillo, 1877)

Oxystele romettensis Granata-Grillo, 1877: 5.

Cirsonella romettensis: Warén, 1992: 160, figs 4C, 9E,

11C-E, 12A

Material examined.- ROCKAL BANK: Hermes 2006/St.65, 1087 m.

Ganesa nitidiuscula Jeffreys, 1883

(Figs 7-14)

Ganesa nitidiuscula Jeffreys, 1883: 94, plate 19 fig. 9

Ganesa nitidiuscula: Warén, 1992: 176, fig. 33A

Description.-

A description has been added because a fresh

shell has been imaged for the first time with a

SEM photograph and additional shell details

can be provided. Warén (1992) figured only a

fragmentary topotype without apex; the

authors have not studied this shell.

The skeneid shell is small, globose,

firm and glossy. Outline is slightly

cyrtoconoid. Height 1.91 mm, width 1.51 mm.

Protoconch of slightly more than 1 whorl has a

dimension of 230 x 173 μm with a rough

surface structure consisting of irregularly

shaped grains of 2-10 μm. Transition to the

teleoconch is marked by a clear varix.

Teleoconch has 3.2 well-rounded smooth

whorls with occasionally a growth line. Suture

is very shallow; the joint to the preceding

whorl is slightly sloping downwards. Above

and below the suture, a remarkable etched

band is visible as a line on the

microphotograph but it is not visible with a

normal stereomicroscope. This bands ends

abruptly at the anal side of the aperture. The

umbilicus is very narrow without umbilical

groove. Outer lip is sharp and prosocline below

the suture; then follows a straight line until the

periphery of the whorl; finally, with a marked

curve leading to the basal part of the lip under

nearly 100º. A basal view clearly shows the

prosocline aperture developing in a straight

line from the centre to the periphery of the

whorl. Callus is developed along the lip but is

nearly absent along the columella. The surface

appearance is smooth and glossy. Colour is

translucent cream white.

Locality.-

Hermes 2005/23, N55.50337-W15.78590,

depth 667 m, upper SE flank of the Rockall

Bank, one empty shell. The sediment sample

contained fine biogenic silty clay. Living fauna

included the corals Madrepora and Stylaster as

well as Actiniaria, Bryozoa, Tunicata and

Bivalvia; dead fauna included Lophelia and

Madrepora corals.

Distribution.-

Jeffreys (1883) reported the species from

between the Hebrides and the Faroes. We add

the Rockall Bank to its distribution.

Mikro hattonensis n. sp.

(Figs 15-22)

Description of the holotype (ZMA Moll.

410023; Figs 15-22).-

Very small and elevated skeneimorph shell

with keeled shoulder. Height 0.795 mm, width

0.767 mm. Inflated protoconch with 1.2 whorls

with a clear transition to the teleoconch but no

varix is present. The surface structure of the

protoconch is eroded but it appears to be

smooth. Diameter of the protoconch is 130 μm.

Teleoconch whorls are well rounded, and show

a keel at the shoulder. A strong radial rib

marks the upper edge of the keel. The start of

the teleoconch shows a remarkably pitted

structure both on the shoulder and on the

immediate area below it. A ventral outline

52


shows a step-wise top, obese shell with a well-

rounded base. Surface texture of the peripheral

area of the body whorl is smooth with many

growth lines. The lip is sharp and slightly

flared at the base. The suture is very shallow;

the shoulder is straight. The umbilicus is open

and deep. The umbilical area forms a wide

spiral funnel with a pronounced elevated radial

ridge at the midst of the columella. The

umbilical area is covered with numerous

elongated pits and with some axial growth

lines. A weak spiral rib marks the umbilical

area. The adjacent area on the body whorl also

shows less frequent pitting. The aperture is

slightly opisthocline at the suture; aperture

plane is slightly curved inwards (concave).

Shell is opaque white.

Variability.-

Variability is poorly mapped. Maximum size is

1.5 mm; recorded from the Rockall Bank

specimen. This specimen was in poor

condition and an alternative shell was selected

for the holotype. The clearly adult specimen

from Rockall has a flared lip / varix.

Type locality.-

Hermes 2008/35, N58.74118 -W18.66255,

depth 796 m, Hatton Bank, holotype is based

on an empty shell. Sediment sample contained

fine carbonate mud. Fauna included corals

(Anthozoa), Ophiuroidea and Polychaeta.

Type material.-

The holotype and one paratype have been

found at the type locality. Moundforce

2004/29, N55.422-W15.611, depth 1443 m,

one worn paratype with height 1.5 mm. All

shells were empty.

Distribution.-

This species is only known from the Hatton

and Rockall Banks.

Etymology.-

The species is named after the type locality.

Discussion.-

Only a single genus in Skeneinae fits our new

species: Mikro Warén, 1996. Mikro

hattonensis is very similar to the type species

Mikro globulus Warén, 1996, which has been

described from Iceland. The keeled outline,

general shape, size and protoconch appear very

similar but the protoconch of our species is

smaller. In M. hattonensis, the radial rib on the

shoulder extends over the full spire and, in

contrast, it fades away on the teleoconch of M.

globulus. Finally, the pitting on top of the

teleoconch and in the umbilical area of M.

hattonensis is absent in M. globulus.

Akritogyra curvilineata Warén, 1992

Akritogyra curvilineata Warén, 1992: 162-163, figs 4F,

13A-D, 15A, 16A-B

Material examined.- HATTON BANK: Hermes 2008/117, depth 958 m, 1

shell.

Akritogyra similis (Jeffreys, 1883)

Cyclostrema simile Jeffreys, 1883: 92, plate 19, fig. 4

Akritogyra similis: Warén, 1992: 161-162, figs 13E-F,

14A-B, 15C



depth 667 m; HATTON BANK: Hermes 2008/59, depth

788 m.

Lissotesta minima (Seguenza, 1876)

Margarites minima Seguenza, 1876: 186.

Lissotesta minima: Warén, 1992: 171-172, figs 25E-F,

29A-C


HATTON BANK: Hermes 2008/117, depth 958 m, 1

shell.

Lissotesta turrita (Gaglini, 1987)

Cyclostrema turritum Gaglini, 1987: 5

Lissotesta turrita: Warén, 1992: 172-173, figs 26B, 30A-

F

Material examined.- ROCKALL BANK: Hermes 2006/65, depth 1087 m.

Anekes affinis (Jeffreys, 1883)

Cyclostrema affinis Jeffreys, 1883: 92, plate 19 fig. 5

Anekes affinis: Warén, 1992: 164-165, figs 18A-B, 19A

53



HATTON BANK: Hermes 2008/36, depth 700 m.

Anekes paucistriata Warén, 1992

Anekes paucistriata Warén, 1992: 165-166, figs 19D,

20B-D, 21A, 22B


Granigyra arenosa Warén, 1993

Granigyra arenosa Warén, 1993: 180-181, figs 18-20

Material examined.- HATTON BANK: Hermes 2008/35, depth 796 m, 2

shells.

Granigyra tenera (Jeffreys, 1883)

(Figs 23-27)

Cyclostrema tenerum Jeffreys, 1883: 91-92, plate 19 fig.

2

Granigyra tenera: Warén, 1992: 176, fig. 33B

Description.-

A description has been provided because a

fresh shell has been imaged for the first time

with a SEM photograph and microstructure

and a protoconch can be displayed.

The elevated skeneimorph shell has a

rugose radial and axial surface structure.

Height 1.1 mm, width 1.2 mm. Protoconch

with 1.1 whorls with a clear transition to the

teleoconch; surface structure is granular with a

few very fine spiral ribs. Size of the

protoconch is 180 x 240 μm.

Teleoconch whorls are very well

rounded, slightly oval towards the base. The

first half whorl of the teleoconch has numerous

axial growth ridges. Then radial ridges are

weaved in at the second teleoconch whorl and

these are ultimately dominating in the body

whorl; spacing between the radial ridges on the

last whorl is about 10-20 μm. The outline is

rather inflated ending in a well-rounded base.

The outer lip is sharp thin and fragile. The

suture is deep initially but rather shallow in the

body whorl; the joint is nearly perpendicular to

the previous whorl. Umbilicus is narrow, deep

but tortuous. Regular spiral ribs and axial

ridges cover the umbilical area. Aperture is

slightly prosocline, nearly orthocline with a

slight bend in the lip. Shell is translucent

white.

Locality.-

Hermes 2006/65, carbonate mud with coral

debris, N55.452-W15.766, depth 1087 m,

Rockall Bank, one empty shell.

Retigyra millipunctata (Friele, 1886)

Cyclostrema millipunctatum Friele, 1886: 33, plate 11

figs 17, 18, 18a

Retigyra millipunctata: Warén, 1989: 6, figs 5A-E

Material examined.- HATTON BANK: Hermes 2008/36, depth 700 m;


Xyloskenea naticiformis (Jeffreys, 1883)

Cithna naticiformis Jeffreys, 1883: 112, plate 20 fig. 11

Xyloskenea naticiformis: Warén, 1996: 202-205, figs 3A-

D, 7C


1 eroded shell.

Xyloskenea xenos n. sp.

(Figs 28-33)

Description of the holotype (ZMA Moll.

410024; Figs 28-30).-

Fragile elevated skeneimorph shell with

flattened apex and keeled umbilicus. The

height is 2.9 mm; the width is 3.3 mm. The

protoconch has a typical skeneid form with 1.3

whorls but the surface has been eroded.

Diameter of the protoconch is about 160 μm

and has a smooth surface. Teleoconch has 2.7

whorls that rapidly grow in diameter.

The whorls are well rounded,

somewhat globose, and they show weak yet

clearly visible radial ribs covering the upper

half of the whorls. Outline is flattened at the

top ending in a well-rounded base. The lip is

sharp. The suture is fairly deep. The umbilicus

is open, wide and deep. The umbilical area

shows a pronounced intra-umbilical keel with a

sharp edge leaning towards the umbilical side.

The aperture is prosocline and oval. Surface

texture is fairly smooth with numerous fine

http://www.somali.asso.fr/clemam/biotaxis.php?A=A0825

54


growth lines. Shell is dull and white, even

though the surface of the holotype has been

exposed to erosion.

Variability.-

Variability is poorly known with only few

specimens available. Maximum width is 3.3

mm. The initial whorls of subadult specimens

are more flattened; only the single adult

specimen, i.e. the holotype, shows a body

whorl with a suture well below the periphery

of the penultimate whorl. The inside of the

body whorl of the sub-adults is a bit glossy.

Type locality.-

Hermes 2008/35, N58.74118 -W18.66255,

depth 796 m, Hatton Bank, holotype is based

on an empty shell. Sediment sample contained

fine carbonate mud. Fauna included corals

(Anthozoa), Ophiuroidea and Polychaeta.

Type material.-

The holotype and four paratypes have been

found at the type locality. Hermes 2008/59,

biogenic carbonate mud, N58.78065 –

W18.58983, depth 788 m, one paratype. All

type specimens are empty shells.

Distribution.-

This species is only known from the Hatton

Bank.

Etymology.-

Xyloskenea is known to live on sunken wood

but there has been no mention of recovered

wood from any of the box-core localities. The

current species is considered a stranger (xenos

in Greek) at the type locality.

Discussion.-

The genus Xyloskenea Marshall, 1988 shows

the morphological features of the new species

and they are known to exceed the size of 3 mm

globally. Other genera in Skeneinae seldom

exceed this size in the NE Atlantic, only deep-

water species of the genus Cirsonella Angas,

1877 (like Cirsonella ateles Dautzenberg &

Fischer, 1896) form an exception but these

have a totally different shell. Xyloskenea

naticiformis (Jeffreys, 1883) is the only known

representative of Xyloskenea in the NE

Atlantic; see Warén, 1996. Xyloskenea

naticiformis is known from off Iceland and off

Portugal. The authors have also found this

species on the Rockall Bank. An obvious keel

at the base of the whorl can easily distinguish

X. naticiformis from X. xenos. The former

also lacks the weak radial rib structure.

Palazzia ausonia (Palazzi, 1988)

Omalogyra ausonia Palazzi, 1988: 103

Palazzia ausonia: Warén, 1991: 75-77, figs 17A-G, 18A

Material examined.- ROCKALL BANK: Hermes 2006/65, 1087 m.

Palazzia planorbis (Dall, 1927)

Lippistes planorbis Dall, 1927: Art. 18, 131

Palazzia planorbis: Warén, 1991: 75-77, figs 16A-D,

18B


Hermes 2006/10C, depth 587 m; Hermes 2006/12, depth

1091 m; Hermes 2006/65, 1087 m.

Eudaronia aperta (Sykes, 1925)

Omalogyra aperta Sykes, 1925: 192

Eudaronia aperta: Warén, 1991: 80, figs 14C-E, 18D


Adeuomphalus ammoniformis Seguenza, 1876

Adeuomphalus ammoniformis Seguenza, 1876: 10

Adeuomphalus ammoniformis: Kano, Chikyu & Warén

2009: 401-403, figs 1F-I


Adeuomphalus densicostatus

(Jeffreys, 1884)

Homalogyra densicostata Jeffreys, 1884: 129, plate 10

fig. 1

Adeuomphalus densicostatus: Kano, Chikyu & Warén

2009: 403-404, figs 1A-E


Hermes 2006/12, depth 1091 m; HATTON BANK:


55


Cantrainea globuloides

(Dautzenberg & Fischer, 1896)

Leptothyra globuloides Dautzenberg & Fischer H. 1896:

175, plate 21 fig. 1

Material examined.- HATTON BANK: Hermes 2008/117, depth 958 m.

REFERENCES

Dall W. H., 1927. Small shells from dredgings

off the southeast coast of the United States by

the United States Fisheries Steamer

"Albatross", in 1885 and 1886. Proceedings of

the United States National Museum 70 (18):

1-134

Dautzenberg P. & H. Fischer, 1896. Dragages

effectués par l'Hirondelle et par la Princesse

Alice 1888-1895. 1. Mollusques Gastropodes.

Mémoires de la Société Zoologique de France

9: 395-498

Duineveld, G. C. A [editor], 2006.

Biodiversity, ecosystem functioning and food

web complexity of cold water coral reefs in

the NE Atlantic (Rockall Bank). Cruise

64PE249, Galway-Oban, 19 June – 7 July

2006. Texel: NIOZ. 25 pp. (excluding

appendices)

Friele H., 1876. Bidrag til Vestlandets

Molluskenfauna. Forhandlinger I Viden-

skapsselkabet I Kristiania 1875: 57-64

Friele H., 1877. Preliminary report on the

Mollusca from the Norwegian North Atlantic

Expedition in 1876. Nyt Magazin for

Naturvidenskaberne 23: 1-10

Friele H., 1879. Catalog auf der norwegischen

Nordmeer-expedition bei Spitzbergen

gefundenen Mollusken. Jahrbücher der

Deutschen Malakolozoologischen Gesell-

schaft 6: 264-286

Friele H., 1886. The Norwegian North

Atlantic Expedition 1876-1878, Third

Volume, Zoology, Mollusca II. Christiania:

Grøndahl & Søn, 44 pp.

Granata-Grillo G., 1877. Descriptions de

quelques espèces nouvelles ou peu connues.

Napoli: Salvatore Marchese. 16 pp.

Hoffman, L., B. van Heugten & M. S. S.

Lavaleye, 2008. A new genus and four new

species in the family Skeneidae (Gastropoda)

from the Rockall Bank, northeastern Atlantic

Ocean. Miscellanea Malacologica 3: 39-48

Jeffreys J. G., 1877. New and peculiar

Mollusca of the Patellidae and other families

of Gastropoda procured in the Valorous

expedition. Annals and Magazine of Natural

History (4)19: 231-243

Jeffreys J. G., 1883. On the Mollusca procured

during the H. M. S. "Lightning" and

"Porcupine" expedition. Proceedings of the

Zoological Society of London: 88-115

Jeffreys J. G., 1884. On the Mollusca procured

during the H. M. S. "Lightning" and

"Porcupine" expedition. Proceedings of the

Zoological Society of London: 111-149

Lavaleye, M. S. S. [editor], 2008. HERMES

2008 Coralfish2008, Belgica Mound

Province, Hatton Bank, Cruise Report

64PE291-292, Texel-Cork-Texel, 10-June –

16 July 2008. Texel: NIOZ. 90 pp.

Mienis, F. & H. de Haas [editors], 2004. The

distribution, morphology, sedimentology and

watermass characteristics of and around

mounds in the Gulf of Cadiz and at the SW

Rockall Trough Margin. Cruise report, R.V.

Pelagia, Moundforce 2004 (64PE229), 15

August - 9 September. Texel: NIOZ. 99 pp.

Odhner, N. H., 1912. Northern and Arctic

Invertebrates in the Collection of the Swedish

State Museum. Prosobranchia, 1. Diotocardia.

Kungliga Svenska Ventenskapsakaemiens

Handlingar 54 (1): 1-274

Palazzi, S., 1988. Note sugli Omalogyridae

mediterranei e maderensi. Bollettino Mala-

cologico 24: 101-111

Rubio, F., L. Dantart & Á. A. Luque, 1998.

Two new species of Dikoleps (Gastropoda,

56


Skeneidae) from the Mediterranean coast of

Spain. Iberus 16: 81-93

Rubio, F., L. Dantart & Á. A. Luque, 2004. El

género Dikoleps (Gastropoda, Skeneidae) en

las costas ibéricas. Iberus 22: 115-132

Sars G. O., 1878. Bidrag til kundskaben om

Norges arktiske fauna: 1. Mollusca regionis

Arcticae Norvegiae. Oversigt over de i Norges

arktiske region forekommende bloddyr. Christiania: A.W. Brøgger, xv + 466 pp.

Seguenza G., 1876. Studii stratigrafici sulla

formazione pliocenica dell’Italia Meridionale.

Bollettino del reale Comitato Geologico

d’Italia 7: 7-15

Van Duil, F. C. & G. C. A Duineveld [editors],

2005. Biodiversity, ecosystem functioning and

food web complexity of deep water coral reefs

in the NE Atlantic (Rockall Bank and

Porcupine Bank). Cruise 64PE238, Galway-

Texel, 21 June – 21 July 2005. Texel: NIOZ.

31 pp. [excl. Appendices]

Warén, A., 1989. New and little known

Mollusca from Iceland. Sarsia 74: 1-28


Mollusca from Iceland and Scandinavia.

Sarsia 76: 53-121


skeneimorph gastropods from the

Mediterranean Sea and the adjacent Atlantic

Ocean. Bollettino Malacologico 27: 149-248


Mollusca from Iceland and Scandinavia, Part

2. Sarsia 78: 159-201

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Mollusca from Iceland and Scandinavia, Part

3. Sarsia 81: 297-245

57


Figs 1-6. Genus Rugulina. 1-3. R. fragilis (G.O. Sars, 1878), Moundforce 2004/37, depth 557 m, Rockall Bank, height 2.2

mm; 1. Ventral view; 2. Basal view; 3. Surface structure body whorl; 4-6. R. species, Hermes 2008/117, depth 958 m, Hatton

Bank, height 2.3 mm; 4. Ventral view; 5. Basal view; 6. Apical view.

58


Figs 7-14. Ganesa nitidiuscula Jeffreys, 1883, Hermes 2005/23, N55.50337-W15.78590, depth 667 m, Rockall Bank, height

1.9 mm, width 1.5 mm; 7. Ventral view; 8. Side view; 9. Apical view; 10. Protoconch 230 x 173 m; 11. Ventral view

(SEM); 12. Side view (SEM); 13. Apical view (SEM); 14. Surface structure protoconch.

59


Figs 15-22. Mikro hattonensis n. sp., holotype, Hermes 2008/35, N58.74118 -W18.66255, depth 796 m, Hatton Bank, height

0.80 mm, width 0.77 mm; 15. Side view; 16. Ventral view; 17. Apical view; 18. Microstructure umbilical area; 19.

Protoconch 200 x 140 m; 20. Ventral view (SEM); 21. Apical view (SEM); 22. Basal view (SEM).

60


Figs 23-27. Granigyra tenera Jeffreys, 1883, Hermes 2006/65, carbonate mud with coral debris, N55.452-W15.766, depth

1087 m, Rockall Bank, height 1.1 mm, width 1.2 mm; 23. Ventral view; 24. Apical view; 25. Basal view; 26. Protoconch 240

x 180 μm; 27. Detail of body whorl structure.

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Figs 28-33. Xyloskenea xenos n. sp. Figs 28-30. Holotype, Moundforce Hermes 2008/35, N58.74118 -W18.66255, depth 796

m, Hatton Bank, height 2.9 mm, width 3.3 mm; 28. Ventral view; 29. Apical view; 30. Protoconch diameter 160 m; 31-33.

subadult paratype, Hermes 2008/59, N58.78065 – W18.58983, depth 788 m, Hatton Bank, width 1.7 mm. 31. Ventral view;

32. Basal view; 33. Apical view.

Skeneimorph species (Gastropoda) from the Rockall and

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