40 



In view of the name Arca radiata having been used by Sowerby in 1 840 ^) for a fossil 

 species, Nyst changed the name of Reeve's species to Arca tricenicosta in 1848. Dunker 

 apparently was not aware of Nyst's work and suggested the name A. philippiana for the same 

 species : this name was adopted by Kobelt in his work with some doubt, while Lamy reverted 

 to Reeve's name A. radiata. 



Kobelt described A. tricenicosta in détail and published a figure of one of Dunker's 

 originals of A. philippina. This species does not vary so much in référence to the contour of 

 the shells, but the sculpture is somewhat variable and differs markedly in shells of différent sizes. 



Distribution : — A. tricenicosta has been recorded from China and Japan. 



In the "Siboga" collection this species is represented by a number of spécimens of 

 différent âges from St. i (7° 27^.5 S., ii3°8'.5E.). Anchorage off Djankar, Java (St. 4), Bay of 

 Bima (St. 47), Macassar (St. 71), West of Kwandang Bay entrance (St. 1 16), Wunoh Bay (St. 152), 

 Waru Bay, north of Ceram (St. 174), Ambon Anchorage (St. 181), Buton Strait (St. 206), 

 Anchorage off Pasir Pandjang, West Coast of Binongka (St. 220), Anchorage east of Dangar 

 Besar, Saleh Bay (St. 313), and St. 318 (6°36'.5S., 1 14° 55'.5 E.). 



10. Arca [Ajiadara] pilula Reeve. 



1843. Arca pilula Reeve, Conch. Icon., II, Arca, pi. II, fig. 8. 



1844. Arca pilula Reeve, Proc. Zool. Soc. London, p. 39. 



1845. Arca pilida Catlovv & Reeve, Conch. Nomencl., p. 50. 

 1848. Arca pihda Nyst, Mém. Acad. Roy. Belgique, XXII, p. 56. 



1857. Arca [Scdipharca] pilula Adams, H. & A., Gen. Rec. Moll., II, p. 538. 



1860. Arca pilula Reeve, Elem. Conch., II, p. 93. 



1887. Arca (Anadara) pilula von Marten.s, Journ. Linn. Soc. London (Zool.), XXI, p. 208. 



1889. Arca [Anomalocardia) pilula Kobelt in Martini Chemn. Conch. -Cab. (N. F.), VIII (2), 



Arca, p. 108, pi. XXVIII, figs. 7, 8. 



1890. Scapliarca pilula Paetel, Cat. Conch. Samm., III, p. 217. 

 1896. Scapliarca pilula Casto de Elera, Cat. Sist. Filip., p. 805. 

 1905. Arca pilula Hidalgo, Cat. Filip., p. 374. 



1907. Arca [Cunearca] pilula Lamy, Journ. Conchyliol., LV, p. 275. 



1909. Arca [Cunearca] pilula, Lamy, Bull. Mus. d'Hist. Nat. Paris, XV, p. 467. 



19 10. Arca pilida Hedley, Austral. Ass. Adv. Sci., XII, p. 344. 



191 1. Arca [Cunearca] pilida Pelseneer, "Siboga" Lamellibranches (Anat.), pp. 10 — 12, 14, 



pi. III, fig. 2. 



I can not agrée with Lamy that A. pilula Reeve is a member of the subgenus Cune- 

 arca Dali, and in spite of its slightly inequivalve shell I believe that it is a true Anadara. 



The right valves hâve in the middle 6 — 10 ribs smooth, while the anterior and posterior 

 ribs are, like those of the left valve, finely nodulose. The shells collected by the "Siboga" 

 Expédition are ail young spécimens, and are slightly higher than long. The measurements of 

 one of thèse spécimens are: — Length 14.4mm., height 15.2 mm., diameter 13.5 mm. 



Distribution : — A. pihila was described from the Island of Burias, Philippines, and has 

 since been recorded from New Caledonia, Java, Mergui and Ceylon. 



In the "Siboga" collection this species is represented by one complète shell and a number 

 of odd valves collected off Djangkar, Java (St. 4). 



i) Sowerby, G. B. — Trans. Geol. Soc. London, V. p. 2, pi. XXV, fig. 12 (1840). 



