23 



N. [T.) ramsayi^ but teeth sharper and more closely placed ; a low, curved, longitudinal internai 

 ridge présent. Shell of yellovvish brown colour, nacre shining white. 



Measurements of Holotype : — Length 7.5 mm., height 4 mm., diameter 2 mm. 



Habitat: — The "Siboga" collection contains the Holotype and an odd valve brought 

 up in a deep-sea trawl at St. 52 (9°3'.4S., ii9°56'.7E., 959 mètres). 



Remarks: — iV. (7".) elaborata is allied to N. {T.) ramsayi (Smith) and N'. [T.) viodica 

 Prashad, but is distinguished from either by its form, sculpture and hinge. 



1 1. Nticzilana [Poroledci) parallelodonta sp. nov. (Plate I, figs. 35, 36, and Plate VIIl, fig. i,"). 



The following is a description of this new species : — Shell médium sized, oblong, 

 rostrate, thin, shining, translucent ; rounded anteriorly, with a narrow elongate beak posteriorly ; 

 very inequilateral ; distinct, slightly raised, acute umbones in anterior third of shell ; anterior 

 dorsal slope short -, posterior more than twice as long, very concave, evenly arched ; sculpture 

 consisting of very low, almost microscopic concentric striae, with two obscure radial ribs and 

 a shallow groove running in between ; hinge-plate very weak, feebly developed, consisting of 

 elongate, thin, lamellar teeth placed parallely and forming obtuse angles with shell margin, 7 in 

 anterior and 4 in posterior part of hinge. Shell of light straw colour ; nacre shining white. 



Measurements of Holotype : — Length 13.3 mm., height 5.4 mm., diameter 2.4 mm. 



Habitat: — The unique Holotype was dredged at St. 226 (5°26'.7S., i27°36'.5E., 

 1595 mètres). 



Remarks : — N . (P.) parallelodonta is allied to N. {P.) spathula (Hedley) ^), but is 

 distinguished by its much broader shape, less arched rostrum and more feebly developed hinge teeth, 



12. Nuculana [Poroleda) sibogaensis sp. nov. (Plate I, fig. 37). 



N. {P.) sibogaensis is represented by two slightly damaged left valves only, and I, there- 

 fore, refrain from giving a detailed description of the species. It is closely allied to A^. {P.) 

 parallelodonta Prashad described above, but is easily distinguished by its more elongate and 

 spathulate valves, much thicker shell, less prominent umbones, and better developed hinge, 

 which consists of 12 teeth in the anterior and 6 in the posterior part of the hinge. The sculpture 

 is slightly more pronounced. 



Measurements: — length 18.8 mm., height 6 mm., diameter 6 mm. 



Habitat : — Two left valves of this interesting species were brought up in a deep-sea 

 trawl at St. 178 (2°4o'S., i28°37'.5E., 835 mètres). 



13. Nuculana i^ Ledella) discrepaîis sp. nov. (Plate I, figs. 38, 39). 



The following is a description of this new species : Shell small, thick, ovate, inequilateral, 

 ornamented with very regular, thin, concentric striae, much narrower than interspaces ; obtusely 

 rounded anteriorly, slightly rostrate posteriorly, rostral area marked by a distinct groove running 

 to ventral margin from near umbo ; umbones somewhat tumid, prominent, turned inwards and 



i) Hedley, C. — Proc. Linn. Soc. N. S. Wales, XXXIX, p. 696, pi. LXXVIII, figs. 17, 18 (1915). 



