DEEP-SEA PROTOBRANCHIA (BIVALVIA) 



69 



▲ 



3 



Fig. 109 Yoldiella jeffreysi . Length frequency histogram superimposed by a gonadial index. 1, immature, no gonadial development seen in 

 the intact specimen; 2, first sign of gonadial development at ventral edge of visceral mass; 3, gonad surrounds the periphery of the visceral 

 mass; 4, gonad covers half the visceral mass; 5, visceral mass wholly covered by gonad. Top, females; bottom, males. 



specimen a few eggs were present in the mantle cavity. This is 

 not taken as evidence of brooding. 



It is clear that Yoldiella enata and Yoldiella ella are very 

 closely related, however, we have no difficulty in distinguis- 

 ing them from their shell features. It should also be noted that 

 the depth distribution of the two species is very different, 

 Yoldiella enata is found on the lower slope while Yoldiella ella 

 is truly abyssal. 



Yoldiella ella (new species) 



Type locality. R.V. Chain Sta. 334, North America Basin, 

 30.9.1972, 40°42.6'N, 46°13.8'W - 40°44.0'N, 46°14.6'W, 

 Epibenthic Trawl, 4400 m. 



Type specimen. Holotype: BM(NH) 1992034. Paratypes in 

 collection held by J. A. Allen. 



? ig. 110 Yoldiella enata. Lateral view of a shell from the right side 

 and detail of the hinge-plate of a left valve. Specimen from Sta. 

 301, Guyana Basin. (Scale = 1.0 mm). 



how the same number of coils. In a specimen 3.1 mm the 

 palps, which are moderately small, have 14 internal ridges. 

 The palp proboscides are large and broad. The kidney is large 

 ind extends anteriorly lateral to the stomach. The largest 

 pecimens are mature and in the case of one sectioned 



Material 



















Cruise 



Sta 



Depth 



No 



Lat 



Long 



Gear Date 







(m) 















NORTH AMERICA BASIN 













Atlantis II 



12 

 Chain 50 



72 



2864 



1 



38°16.0'N 



71°47.0'W 



ET 



24. 



8.64 



76 



2862 



1 



39°38.3'N 



67°57.8'W 



ET 



29. 



6.65 





78 



3828 



5 



38°08.0'N 



69°18.7'W 



ET 



30. 



6.65 





85 



3834 



11 



37°59.2'N 



69°26.2'W 



ET 



5. 



7.65 



Atlantis II 



126 



3806 



4 



39°37.0'N 



66°47.0'W 



ET 



24. 



8.66 



24 









- 39°37.5'N 



66°44.0'W 









Chain 106 



334 



4400 



44 



40°42.6'N 

 - 40°44.0'N 



46<T3.8"W 

 46°14.6"W 



ES 



30. 



8.72 



