333 

 13- Ciispidaria [Cardiomya) semicostata sp. nov. (Plate VII, figs. 47, 48). 



The following is a description of this new species : — Species of a small size ; shell 

 SLibglobose, greatly inflated, shortly rostrate, thin ; subtruncate in front, round posteriorly with 

 a short triangular rostrum behind ; umbones inflated, rounded, curved inwards and forwards, 

 approximating in middle, sHghtly raised above hinge-line ; anterior and posterior dorsal margins 

 straight, ventral border only slightly arcuate ; sculpture co nsisting of very regular, close-set, 

 rounded, microscopic, concentric striae and 3 main strongly developed hollow radial ribs on 

 posterior third of shell ; alternating with thèse are 3 — 4 less developed radial ribs and 6 — 7 

 moderately strong radial ribs on rostrum. Shell of a duU milk white colour. 



Measurements of Holotype : — Length 10.2 mm., height 8.4 mm., diameter (single left 

 valve) 3.8 mm. 



Habitat : — Two complète left and a damaged right valve of this species were brought 

 up in a trawl at St. 159 (o'59^iS., i29°48'.8E., 411 mètres). 



Remarks: — C. (C) semicostata is allied to C. (C) forticostata Sowerby ^) from Cape 

 Natal, but the short triangular rostrum and the radial sculpture confined to the rostrum and 

 posterior third of the shell of the former distinguish it at once from the African species. 



14. Cuspidaria {Rhinoclamd) dubia sp. nov. (Plate VII, figs. 49, 50). 



The following is a description of this new species : — Species of a small size, shell 

 elongately pyriform, inequilateral, moderately inflated, thin; rounded in front, acuminated and 

 shortly rostrate behind; umbones rather depressed, situated in front of middle of shell, smooth; 

 anterior dorsal margin slightly convex, posterior dorsal somewhat concave; ventral margin 

 arcuate, somewhat sinuated posteriorly to form the ventral margin of narrow rostrum ; rostrum 

 short, compressed, truncated, with well developed ridge running from umbones to its lower 

 angle ; sculpture consisting of regular concentric thread-like raised striae separated by broad inter- 

 spaces; left valve edentulous, right with anterior and posterior laterals, posterior better developed, 

 no fossette, resilium inserted under umbones. Shell of a light straw colour, nacre whitish. 



Measurements of Holotype: — Length 7.5 mm., height 4.8 mm., diameter 3.4 mm. 



Habitat: — The Holotype and a few stray valves of this new species were brought 

 up in deep-sea trawls at St. 211 (5°4o'.7S., i20°45'.E., 1158 mètres) and St. 221 (6° 24' S,, 

 i24°39'E., 2798 mètres). 



Remarks : — C. [R}j dtibia appears to be allied to C. (7?.) rugata ^) A. Adams, but the 

 form of the shell and the sculpture of the two species are différent. 



15. Cuspidaria [Pseudoneaerd) thatimasia Sturany. 



190 1. Pseudoneaera thauniasia Sturany, Denkschr. Kais. Akad. Wiss. Wien, Math.-Nat., LXIX, 

 p. 265, pi. XI, figs. II — 16. 



A single shell with the right valve damaged from "Siboga" St. 306 agrées so closely 



i) SowERCY, G. B. — Mar. Investigations in S. Africa, IV, p. i8, pi. VII, fig. 15 (1904). 

 2) Adams, A. — Ann. Mag. Nat. Hist., (3) XIII, p. 208 (1864). 



