152 



i868. Isocardia [Meiocardia) tetragona Romer in Martini-Chemn. Conch.-Cab. (N. F.), X (2), 



Cardiacea, p. 10. 



1882. Isocardia tetragona Dunker, Ind. Moll. Mar. Japon., p. 213. 



1884. Isocardia tetragona Grasset, Ind. Test. Viv., p. 273. 



1890. Isocardia {Meiocardia) tetragona Paetel, Cat. Conch. Samm., III, p. 120. 



1895. Isocardia tetragona Pilsbry, Cat. Mar. Moll. Japan, p. 130. 



1906. Isocardia tetragona Owston, Japan. Loochooan Shells, p. 35. 



[920. Isocardia [Meiocardia') tetragona Lamy, Journ. Conchyliol., LXIV, p. 300. 



The shells of /. [M^ tetragona are quadrate, being much longer than high. The posterior 

 ridge is neither very sharp nor very raised in the adult shells, and the sculpture consists of 

 somewhat irregular, distantly placed, concentric ribs. I figure a full-grown shell from the 

 "Siboga" collection. 



Distribution : — /. {^^'I^ tetragona has so far been recorded from round Japan. 



The "Siboga" dredged several shells on the Bank between the Islands of Bahuluwano- 

 and Tambolungan, south of Saleyer (St. 66), St. 95 (5°43'.5 N., ii9°4o'E., 522 mètres) and 

 St. 105 (6°8'N., 121° 19' E., 275 mètres). 



Family Vesicomyidae. 



Genus Vesicomya Dali. 



1886. Vesicomya Dali, Bull. Mus. Comp. Zool. Harvard, XII, p. 272. 



1900. Vesicomya Smith, Proc. Malacol. Soc. London, IV, pp. 81 — 83, fig. 11. 



1920. Vesicomya Lamy, Journ. Conchyliol., LXIV, p. 302. 



Dall introduced the name Vesicomya in a subgeneric sensé with Callocardia [Vesicomya^ 

 atlantica Smith as the type. Smith in the paper cited, described and figured the hinge of V. lepta^ 

 and published a list of the species which should be separated under the generic name Vesicomya. 



I. Vesicomya solidissima sp. nov. (Plate IX, figs, i — 4). 



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

 elongate-ovate, very inequilateral, greatly swoUen ; white ; anterior side narrow, rounded ; posterior 

 broadly rounded; ventral margin somewhat arcuate; umbones moderately prominent, incurved, 

 subcontiguous, situated at about ^4 of total length from anterior margin; lunule very prominently 

 marked, cordate, carinated in the middle; sculpture consisting of concentric, low striae running 

 obliquely upwards from about the middle-, hinge normal Vesicomya-\.y'^ç.. Colour of shell dull 

 yellow; inner surface chalky white. 



Measurements of Holotype: — Length 65 mm., height 42.5 mm., diameter 40.5 mm. 



Habitat: — The unique Holotype was brought up in a deep-sea trawl at St. 18 (7° 28'. 2 S., 

 1 15° 24^.6 E., 1018 mètres). 



Remarks : — V. solidissima is very closely allied to V. indica Smith ^), but is easily 

 distinguished by its much more elongate and more swollen shell and the very narrow, rounded 

 anterior side. 



i) Smith, E. A. — Ann. Mag. Nat. Hist., (7) XIV, p. 9 (1904), and lUuslr. Zool. "Investigator", Moll., pi. XVII, figs. 4, 4rt—<r (1907). 



