DEEP-SEA PROTOBRANCHIA (BIVALVIA) 



Yoldiella robusta (new species) 



Type locality. R.V. Atlantis II, Cruise 60, Sta. 280, 

 Argentine Basin, 29.3.1971, 36°18.0'S, 53°23.9'W, 

 Epibenthic Trawl, 256-293 m. 



39 



Type specimen. Holotype : BM(NH) 1992030, Paratypes: in 

 collection held by J. A. Allen. 



Material. 



Cruise Sta Depth No Lat Long 



(m) 



Gear Date 



Fig. 54 Yoldiella frigida. Lateral view from the right side of the 

 internal morphology of a specimen from Sta. 105 North America 

 Basin. Inset is a right-frontal external view of the stomach. (Scale 

 = 1.0 mm). For identification of parts see Figs. 34 & 49. 



ig. 55 Yoldiella robusta. Lateral view of a shell from the right 

 side and detail of hinge-plate of a left valve. Specimens from Sta. 

 280 Argentine Basin. (Scale = 1.0 mm). 



ARGENTINE BASIN 

 Atlantis II 280 256- 3495 36°18.0'S 

 293 



53°23.9'W ES 29.3.71 



Restricted to one Station at the shelf/slope break of the 

 Argentine Basin. Depth range: 256-293 m. 



Shell description (Figs. 55 & 56). Shell subovate, moder- 

 ately inflated, irregular concentric growth lines and small 

 ridges best developed posteriorly, periostracum pale yellow; 

 umbos anterior to mid line, slightly raised and inwardly 



Fig. 56 Yoldiella robusta. Outlines of shells from the right side to 

 show change in shape with growth. Specimens from Sta. 280 

 Argentine Basin. (Scale = 1.0 mm). 



Fig. 57 Yoldiella robusta. Lateral view from the right side of the 

 internal morphology of a specimen from Sta. 280 Argentine 

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



