30 



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



with very small anterior and posterior marginal extensions of 

 fused periostracum. 



Internal morphology (Fig. 38). Exhalent and inhalent 

 siphons combined, the inhalent siphon is shorter than the 

 exhalent and open at the ventral margin. There is a siphonal 

 tentacle to the left side. The posterior adductor muscle is oval 

 and approximately half the size of the crescent-shaped ante- 

 rior muscle. The gills are moderately well-developed and the 

 plates number up to 16. The labial palp ridges number 

 between 14-18 depending on size of individual. The foot is 

 large with a conspicuous byssal gland. There is a single hind 

 gut loop to the right of the body which has a characteristic 

 course that approaches an 'S' in shape. 



Prodissoconch length: 198 (xm. Maximum recorded shell 

 length: 5.61 mm. 



Most closely resembles Y. sinuosa but without the postero- 

 ventral sinuosity (Fig. 139). 



Fig. 36 Yoldiella blanda. Lateral view of a shell from the right side 

 and detail of the hinge-plate of a right valve. Specimens from Sta. 

 242 Argentine Basin. (Scale = 1.0 mm). 



Fig. 37 Yoldiella blanda. Outline drawings of shells of differing 

 sizes from the right side to show change in shape with growth. 

 Specimens from Sta. 242 Argentine Basin. (Scale = 1.0 mm). 



Fig. 38 Yoldiella blanda. Lateral view from the right side of the 

 internal morphology of a specimen from Sta. 242 Argentine 

 Basin. (Scale = 1.0 mm). For identification of parts see Fig. 34. 



Yoldiella biscayensis (new species) 



Type locality. R.V. Chain, Cruise 106, Sta. 326, Bay of 

 Biscay, 22.8.1972, 50°04.9'N, 14°23.8'W, Epibenthic Trawl, 

 3859 m. 



Type specimen. Holotype BM(NH) 1992024, Paratypes: in 

 collection held by J.A. Allen. 



Material. 



Cruise 



Sta 



Depth No 

 (m) 



Lat 



Long 



Gear Date 



WEST EUROPEAN BASIN 



Jean Charcot 













(Polygas) 



DS20 4226 



10 



47°33.0'N 



9°36.7'W 



DS 



24.10.72 





DS21 4190 



6 



47°31.5'N 



9°40.7'W 



DS 



24.10.72 





DS22 4144 



21 



47°34.1'N 



9°38.4'W 



DS 



25.10.72 





DS23 4734 



17 



46°32.8'N 



10°21.0'W 



DS 



26.10.72 



(Biogas II) 



DS31 2813 



11 



47°32.5'N 



9°04.2'W 



DS 



19. 4.73 



(Biogas III) 



DS44 3992 



4 



47°33.2'N 



9°42.0'W 



DS 



27. 8.73 





DS41 3548 



20 



47°28.3'N 



9°07.2'W 



DS 



26. 8.73 





DS45 4260 



6 



47°33.9'N 



9°38.4'W 



DS 



27. 8.73 





DS48 4203 



2v 



44°29.0'N 



4°54.0'W 



DS 



31. 8.73 



(Biogas IV) 



DS53 4425 



11 



44°30.4'N 



4°56.3'W 



DS 



19. 2.74 





DS54 4659 



20 



46°31.1'N 



10°29.2'W 



DS 



21. 2.74 





DS55 4125 



76 



47°34.9'N 



9°40.9'W 



DS 



22. 2.74 





DS56 4050 



1 



47°32.7'N 



9°28.2'W 



DS 



23. 2.74 





DS59 2790 



3 



47°31.7'N 



9°06.2"W 



DS 



24. 2.74 





DS60 3742 



24 



47°26.8'N 



9°07.2'W 



DS 



24. 2.74 





KR35 4140 



1 



47°26.0'N 



9°08.7'W 



KR 



25. 2.74 



(Biogas V) 



DS66 3480 



31 



47°28.2'N 



9°00.0'W 



DS 



16. 6.74 





DS67 4150 



4 



47°31.0'N 



9°35.0'W 



DS 



17. 6.74 





DS68 4550 



2+2v 46°26.7'N 



10°23.9'W 



DS 



19. 6.74 





DS69 4510 



1 



44°21.9'N 



4°52.4"W 



DS 



20. 6.74 





DS70 2150 



1 



44°08.8'N 



4°17.4'W 



DS 



21. 6.74 



(Biogas VI) 



DS74 2777 



7 



47°33.0'N 



9°07.8'W 



DS 



22.10.74 





DS75 3250 



9 



47-28.1'N 



9°07.8'W 



DS 



22.10.74 





DS76 4228 



101 



47°34.8'N 



9°33.3'W 



DS 



23.10.74 





DS77 4240 



11 



47°31.8'N 



9°34.6'W 



DS 



24.10.74 





DS78 4706 



47 



46°31.2'N 



10°23.8'W 



DS 



25.10.74 





DS79 4715 



106 



46°30.4'N 



10°27.1'W 



DS 



26.10.74 





DS80 4720 



19 



46°29.5'N 



10°29.5"W 



DS 



27.10.74 





DS81 4715 



9 



46°28.3'N 



10°24.6'W 



DS 



27.10.74 





DS82 4462 



27 



44°25.4'N 



4°52.8'W 



DS 



29.10.74 





