DEEP-SEA PROTOBRANCHIA (BIVALVIA) 



25 



Fig. 25 Yoldiella bilanta. Lateral views 

 of three shells from the right side and 

 internal view of a left valve to show the 

 hinge-plate. Specimens from Sta. 192 

 Cape Basin. (Scale = 1.0 mm). 



50 



W/L 



•; ••»*. 



30 J 

 80 



60 

 60 

 50 



H/L 



PL/TL 



Length(mm) 



Fig. 26 Yoldiella bilanta. Variation in 

 the ratios of height H/L, width W/L, 

 and postero-umbonal length PL/TL to 

 length against length of samples from 

 Sta. 191 (open triangles) and Sta. 192 

 (closed circles) Cape Basin. 



anteriorly directed foot. The lateral papillae of the foot are 

 not so well-developed as those in Y. capensis. 



The specimens from the Cape Verde Basin are somewhat 

 smaller and have a slightly deeper shell than those from the 

 Cape Basin. There appear also slight differences in the size of 

 the posterior adductor muscle and the gills, but these may be 

 a result of distortion following preservation. Such small 

 differences are within the normal variation of yoldiellid 

 species and at most represent a population difference. 



Yoldiella artipica (new species) 



Type locality. R.V. Atlantis II, Cruise 42, Sta. 200, 

 Angola Basin, 22.5.1968, 9°43.5'S, 10°57'0E - 9°41.0'S - 

 10°55.0'E, Epibenthic Dredge, 2644-2754 m. 



Type specimen. : Holotype: BM(NH) 1992021, Paratypes: 

 in collection held by J. A. Allen. 



Material. 



Cruise Sta Depth No Lat Long Gear Date 



(m) 



ANGOLA BASIN 



Atlantis II 200 2644- 25 9°43.5'S 



42 2754 - 9°41.0'S 



Walda DS20 2514 2 2°32.0'S 



10°57.0'E ES 22.5.68 



10°55.0'E 



8°18.1'E ES -.-.71 



Restricted to the abyssal rise of the south east Atlantic. 

 Depth range: 2514-2754 m. 



