2 I 6 



is almost smooth. The periostracum is very shining, of a varnished, fulvous colour, with white 

 and chocolaté spots in the umbonal area. The species is closely allied to M. florida (Lam.), 

 but it never attains the size of that species, and differs in outHne, sculpture and colour. 



Distribution : — M. phasianella was described from shells without a definite locality, but 

 the species has since been recorded from Japan, the Philippines and the Persian Gulf. 



In the "Siboga" collection it is represented by a good séries of shells from the Bornéo 

 Bank (St. 80), Anchorage off Lirung, Salibabu Island (St. 133), Saleyer Anchorage (St. 213), 

 Banda Anchorage (St. 240), Kulewatti Bay, Dammer Island (St. 277), Rumah-Kuda Bay, Roma 

 Island (St. 279) and Anchorage east of Dangar Besar, Saleh Bay (St. 313). 



A full-grown shell of a cream colour with a few brownish spots in the umbonal région 

 collected at Tuai Anchorage, Kei Islands (St. 258), also belongs to this species. 



2. Macrocallista roseotincta (Smith). (Plate VI, figs. 3, 4). 



18S5. Cytlierea [Callista] roseotincta Smith, "Challenger" Lamellibranchia, p. 136, pl.I, figs. 6,6a,b. 



1890. Callista roseotincta Paetel, Cat. Conch. Samm., III, p. 70. 



1896. Callista roseotincta Casto de Elera, Cat. Sist. Filip., p. 741. 



1903. Callista roseotincta Hidalgo, Obras Malacol., II, p. 193. 



1905. Callista roseotincta Hidalgo, Cat. Filip., p. 326. 



1928. Meretrix [Callista) roseotincta Faustino, Summary Philippine Mar. Freshvv. MolL, p. 73. 



Two young shells collected at Banda Anchorage (St. 240) agrée in ail respects with 

 Smith's description and the types of M. roseotincta in the British Muséum (Nat. Hist.), London, 

 from the Philippines. The shells hâve two broad rosy-red to chocolaté rays running downwards 

 from the umbones on the insides of the shell. The periostracum of the "Siboga" shells is some- 

 what rubbed off, but the fine, concentric striae on the surface of the shells are présent. 



A shell collected at Rumah-Kuda Bay, Roma Island (St. 279), differs in size and colouration, 

 but agrées in outline, form and sculpture with normal shells of M. roseotincta, and is identified 

 as a worn shell of this species ; I figure this shell. 



M. roseotincta has so far been recorded from the Philippines only, 



3. Macrocallista sp. 



A number of young shells dredged at Banda Anchorage (St. 240) cannot be referred 

 with certainty to any known species of the genus Macrocallista Meek. 



Genus Hysteroconcha P. Fischer. 



1887. Hysteroconcha Fischer, P., Man. Conchyliol., p. 1079. 



1902. Hysteroconcha Dali, Proc. U. S. Nat. Mus., XXVI, p. 354. 



1903. Hysteroconcha Dali, Trans. Wagner Free Inst. Sci. Philadelphia, III, p. 1265. 



1925. Hysteroconcha Woodring, Miocène Mollusks from Bowden, Jamaica, Pelecypods, etc., p. 154. 



I differ from Dall in considering Hysteroconcha as being equal in rank to Pitar Rômer, 

 and not a subgenus of the latter. This course seems fully justified by the différence in the forms 

 of the shells of the two gênera. The génotype is Hysteroconcha dione (Linn.). 



In the "Siboga" collection there are no représentatives of Hysteroconcha s. s.^ and the 



