164 



consists of numerous (over 25) closely placed concentric lamellae ; the very numerous radial 

 lamellae are comparatively feebly developed, but by their intersection with the concentric lamellae 

 give the latter a beaded appearance. The inner margins of the valves are minutely crenulated. 

 The umbones are full, acute and sharply curved forwards and inwards ; the lunule Is 

 hardly impressed. 



Measurements of the Holotype: — Length 8.5 mm., height 8.5 mm., diameter 5.5 mm. 



Habitat: — Two spécimens of D. [B.) hedleyi were dredged at St. 105 (6° 8' N., 121° 19' E., 

 275 mètres). 



7. Dentilucina {Bellucina) Jiedleyi Prashad var. qîiadrata nov. (Plate V, figs. 19, 20). 



A number of spécimens from St. 212 differ from the typical shells of the new species 

 D. {B.) hedleyi described above, in that the shells are larger, more quadrate and more solid; 

 the dorsal anterior and posterior areas more marked, and the sculpture more granular. I propose 

 separating thèse under the varietal name qiiadrata. 



Measurements of Holotype: — Length 10.5 mm., height 10.5 mm., diameter 8.2 mm. 



Habitat : — A number of shells of this new variety were brought up in a deep-sea trawl 

 at St. 212 (5° 54^.5 S., i20°i9'.2E., 462 mètres). 



Family Ungulinidae. 



Genus Diplodonta Bronn. 



183 1. Diplodonta Bronn, Ital. Tertiàr Gebilde etc., p. XII. 



1887. Diplodonta Fischer, P., Man. Conchyliol., p. 1098. 



1901. Diplodonta Dali, Proc. U. S. Nat. Mus., XXIII, p. 792. 



192 1. Diplodonta Lamy, Journ. Conchyliol., LXV, p. 335. 



1925. Diplodonta Woodring, Miocène Mollusks from Bowden, Jamaica, Pelecypods etc., p. 128. 



1930. Taras Stewart, Spécial Publication Acad. Nat. Sci. Philadelphia, N'^'. 3, p. 193. 



Stewart has replaced Diplodonta Bronn by Taras Risso, but as it is doubtful whether 

 even the type-species of the latter, T. antiçtiatus, is one of the Ungulinidae, I follow Lamy in 

 using the generic name Diplodonta. 



The génotype of Diplodonta is D. Inpifuis (Brocchi). 



I. Diplodonta bullata Dunker. 



1865. Diplodonta bullata Dunker, Novitat. Conch., Meeresconch., Supplément, II, p. ^6, pi. XXVI, 

 fig. r. 



Dunker published very good figures and a detailed description of this species from 

 Ceylon. Lynge ^) considered it, however, to be synonymous with D. globosa (Forskâl). I hâve 

 carefully ~ compared the "Siboga" shells, which I assign to D. bitllata with shells of the same 

 size of D. globosa, and am of opinion that the two are quite distinct. The shells of D. bullata 



i) Lynge, H. — D. Kgl. Dansk. Vidensk. Selsk. Skr. Nat. Math., (7) V, p. 175 (1919). 



