DEEP-SEA PROTOBRANCHIA (BIVALVIA) 



63 



loops to the left of the body with a further double loop 

 passing to the left of the stomach into the foot anterior to the 

 stomach. The loops do vary slightly in their extent and 

 curvature. This is similar to the condition in Y. subcircularis, 

 Y. biguttata and Y. ovata but with an additional loop on the 

 right. The hind gut has a typhlosole along its entire length. 

 Fine material similar to that present in the stomach was seen 

 in the digestive diverticula of a number of specimens. The 

 kidney is well-developed. Sexes are separate. 



The maximum diameter of the ovum as observed in sec- 

 tions of females from samples taken in February and August 

 was similar (130 (xm). There seems to be a wide variation in 

 the numbers of ova present. A female collected in August 

 (2.74 mm) had 255 ova while another collected in February 

 (3.09 mm) had only 65 ova. Maturing gonads were recorded 

 for all months sampled. 



Yoldiellajeffreysi (Hidalgo 1877) 



Type locality. H.M.S. Valorous Sta. 16, Iceland Basin, 

 west of Rockall Plateau, south Maury Channel, 55°10'N, 

 25°58'W, 23.8.1875, Dredge, 1785 fm. 



Type specimen. Holotype: not designated; Lectotype: U.S. 

 Natl. Mus., No. 199696 as here designated. 



Leda lata Jeffreys 1876, 1876. p. 431 (in part). 



Leda jeffreysi Hidalgo 1877, p. 396; Jeffreys 1879, p. 579, pi. 



46, Fig. 2; Dall 1881, p. 124; Smith 1885, p. 234; Dautzen- 



berg 1889, p. 75; Dautzenberg & Fischer 1897, p. 204; 



Locard 1898, p. 353. 

 Portlandia jeffreysi Posselt 1898, p. 36. 

 Yoldiellajeffreysi Verrill & Bush 1898, p. 866, pi. 81, Fig. 5, 



pi. 83, Fig. 3. 



A holotype of Y. jeffreysi was never designated but the 



following USNM specimens were identified as syntypes by 

 Waren (1980):- 



No. 1999695, Valorous Sta. 9; No. 199694, and No. 199696, 

 Valorous Sta. 16; No. 199700, Porcupine Sta. 20; No. 

 199701, Porcupine Sta. 16 & 17; No. 199698 Porcupine Sta. 

 30. 



and in the BM(NH):- 



No. 77.11.18.25, Valorous Stas. 9, 12, 13, 16; No. 

 85.11.5.592-593,Porcupine Sta. 31; No. 85.11.5 366-367, 

 Porcupine Sta. 16; No. 85.11.5. 591, Porcupine Sta. 9. 



Jeffreys original specimens were taken from the North 

 Atlantic (Valorous Stations 9, 12, 13 & 16 and from which he 

 described his species Leda lata (Jeffreys, 1896). Unfortu- 

 nately the material from these four 'Valorous' Stations, which 

 we have examined, contains two species of Yoldiella which 

 are, superficially, similar in form (p. ). Furthermore the 1876 

 description is so general that there is nothing to indicate 

 which of the two species Jeffreys chose when he described 

 Leda lata. Thus, we here accept Leda jeffreysi Hidalgo (1877) 

 as the first unequivocal specific designation and which Jef- 

 freys (1879) himself accepted two years later. 



We have also examined specimens referred to as Yoldiella 

 jeffreysi by Verrill & Bush (1898) (USNM, No. 4888) and 

 these clearly differ from Y. jeffreysi s.s. in being stouter, with 

 a more inflated umbo, a broader hinge plate, with teeth of 

 different form and fewer in number. 



Y. jeffreysi is a very widespread species. It occurs from the 

 base of the continental slope to the deepest abyssal depth. In 

 our samples it occurs in the Argentine, Guyana, North 

 America, West European, Canary, Cape Verde & Angola 

 Basins. It has also been recorded from the Gulf of Mexico 

 (2416-2868 m) and from off West Greenland (3200 m) and in 

 the Mediterranean off Palermo. 



Depth range: 2040-4862 m. The depth distribution is 

 similar throughout the Atlantic. 



Fig. 100 Yoldiella insculpta. Transverse section through the 

 'byssal' gland. (Scale = 0.1 mm). Abbreviations see p. 12. 



Material. 















Cruise 



Sta 



DepthNo 



Lat 



Long 



Gear Date 







(m) 













NORTH AMERICA BASIN 











Atlantis II 



64 



2886 



7 



38°46.0'N 



70°06.0'W 



ET 



21. 8.64 



12 



72 



2864 



6 



38°16.0'N 



71°47.0'W 



ET 



24. 8.64 



Chain 50 



76 



2862 



32 



39°38.3'N 



67°57.8'W 



ET 



29. 6.65 





77 



3806 



109 



38°00.7'N 



69°16.0'W 



ET 



30. 6.65 





78 



3828 



57 



38°00.8'N 



69°18.7'W 



ET 



30. 6.65 





84 



4749 



16 



36°24.4'N 



67°56.0'W 



ET 



4. 7.65 





85 



3834 



413 



37°59.2'N 



69°26.2'W 



ET 



5. 7.65 



Atlantis II 



123 



4853 



4 



37°29.0'N 



64°14.0'W 



ET 



22. 8.66 



24 



124 



4862 



1 



37°26.0'N 

 - 37°25.0'N 



59°59.5'W 

 63°58.0'W 



ET 



22. 8.66 





126 



3806 



138 



39°37.0'N 

 - 39°37.5'N 



66°47.0'W 

 66°44.0'W 



ET 



24. 8.66 



Atlantis II 



175 



4667- 



53 



36°36.0'N 



68°29.0'W 



ES 



29.11.67 



40 





4693 







68°31.0"W 







Chain 106 



330 



4632 



155 



50°43.5'N 

 - 50°43.3'N 



17°51.7"W 

 17°52.9'W 



ES 



24. 8.72 





334 



4400 



49 



40°42.6'N 

 _ 40°44.0'N 



46°13.8'W 

 46°14.6'W 



ES 



30. 8.72 





335 



3882- 

 3919 



28 



40°25.3'N 



46°30.0'W 



ES 



31. 8.72 



Knorr 35 



340 



32164- 13 



38°14.4'N 



70°20.3'W 



ES 



24.11.73 



