78 



J.A. ALLEN, H.L. SANDERS AND F. HANNAH 



Jean Charcot DS37 2110 1 47°31.8'N 8°34.6'W DS 24.8.73 



(Biogas III) 



(Biogas IV) CP01 2245 2 47°34.6'N 8°38.8'W CP 25. 2.74 



CANARY BASIN 



Discovery 6704 2129 1 27°44.9'N 14°25.0'W ED 17.3.68 



This is predominantly a northern Atlantic species occurring 

 mostly from 10-200 metres (Ockelmann, 1958). Neverthe- 

 less, there are sufficient past records to confirm the present 

 identifications that at its southern limits it is present at lower 

 slope depths. Perhaps indicative of a temperature/depth 

 relationship. 



Shell description (Fig. 126). Shell moderately stout, 

 ovate, slightly inequilateral, fine concentric lines, with elon- 

 gate lunule and escutcheon, shell very wide dorsally and 

 medially (such that when it rests on a valve the dorsal part is 

 centred so that both umbos are characteristically visible in the 

 lateral view); umbo very large, raised, internally directed, 

 orthogyrate, immediately anterior to midline; antero-dorsal 

 margin joins anterior and antero-ventral margins in a smooth 

 curve, postero-dorsal margin also joins posterior and postero- 

 ventral margin in smooth curve but is more attenuate than 

 anterior margin; hinge plate moderately stout, not quite 

 reaching level with the outer margins of adductor muscles, 

 hinge plate narrows almost to margin below umbo, anterior 

 and posterior hinge teeth equal in number or with one 

 additional on the posterior plate; ligament amphidetic large, 

 globular, extending far ventral to the hinge plate, slight 

 secondary anterior and posterior external extension of fused 

 periostracum. (See Ockelmann 1958, for typical shell dimen- 

 sions). 



Internal morphology (Fig. 127). The combined siphons 

 are short within a relatively shallow siphonal embayment. 

 There is a slender sensory tentacle on the right side. The 

 anterior sense organ and the feeding aperture are not particu- 

 larly well-developed. The adductor muscles are very large, 

 more or less oval in shape the anterior being the larger in size. 

 The gills are slender with approximately 13 plates in a small 

 specimen 14 mm in length. The palps are large with 13 ridges. 

 The foot is small and in the one whole mount contracted to 

 the level of the ventral edge of the palps. There is a small 

 byssal gland. The stomach is large and the hind gut stout, the 

 latter describes a single loop on the right side of the body. 



Portlandia fora (new species) 



Type locality. R.V. Sarsia, Sta. 56, Bay of Biscay, 

 19.7.1967, 43°43.0'N, 3°47.8'W, Epibenthic Trawl, 641 m. 



Type specimen. Holotype: BM (NH) 1992041. Paratypes: in 

 collection held by J.A. Allen. 



Material. 



Cruise Sta Depth No Lat Long Gear Date 



(m) 



WEST EUROPEAN BASIN 



Sarsia 56 641 15 43°43.0'N 3°47.8'W ED 19.7.67 



Only taken from the Bay of Biscay at one Station on the 

 upper slope. Depth 641 m. 



Shell description (Fig. 128). Shell relatively stout, 



Fig. 128 Portlandia fora. Lateral 

 view of a shell from the left side and 

 a dorsal view of the same shell, detail 

 of the hinge-plate of a left valve and 

 lateral views of two small specimens 

 to show variation in shape with 

 growth. Specimens from Sta. S 56, 

 West European Basin. (Scales = 1.0 

 mm). 



