223 



ON TWO APPARENTLY NEW SPECIES OF CORBICULA. 



By the Rev. R. Ashingtost Bullen, B.A., F.L.S., etc. 



Read \2th April, 1901. 



PLATE XXIII. 



The shells which I propose to describe were bought with a large 

 number of specimens of Amphipeplea, Leiopoma, and Mitra episcopalis 

 shells at Stevens', in November, 1898. They are presumably from 

 the Philippine Islands, and, judging by the very eroded state of the 

 larger species, seem to have come from a locality much charged with 

 carbon dioxide, as the slimy and stagnant waters of a mangrove swamp 

 would be. The shells resemble generally C. fluminalis and C. orientals. 

 But the larger specimen is not C. fluminalis, because the nympha? 

 are squarish, whereas those of C. fluminalis are elongated. The smaller 

 specimen is not C. fluminalis, since the rugae near the umbones are not 

 so pronouncedly sulcate as those of the latter. Nor. is it C. oriental is 

 ( —fluminea), because that is less ventricose towards the ventral margin. 

 Mr. E. A. Smith kindly searched among the specimens in the British 

 Museum some months ago, and failed to find a specimen resembling 

 the smaller one. 



The examples now to be described belong to different species, 

 because the external sulci are different, being deeper in the larger and 

 much divided towards the ventral margin. Moreover, the nymphae are 

 squarish in the larger specimen and elongated in the smaller; the 

 serrations on the lateral teeth are situated more on their upper surface 

 in the smaller specimen, and the lateral teeth themselves in the larger 

 are more acute in transverse section ; and in the interior there are 

 striations on the ventral edge of the valves in the smaller, whereas in 

 the larger the striae are more pronounced on the edge of the pallial 

 impression. Lastly, the umbones in the larger are distant (the distance 

 being exaggerated by their erosion), in the smaller they approximate. 



1. COKBICULA SUBTRIANGULARIS, n.Sp. PI. XXIII, Fig. 1. 



Testa subtriangularis, crassa, inflata, aequivalvis, intus parum albido- 

 fusco-ianthina, extus nigro-castanea, rugis niultis externis transversis 

 aliquantulum elatis, prope marginem ventralem maxime rugosis, laevi- 

 oribus in regione centrali ; pagina interna extra pallii lineam radiatim 

 striata; dentibus cardinalibus 3, lateralibus 2, tenuiter striatis ; liga- 

 mento longitudine 4 mm. ; nymphis subquadratis ; umbonibus rectis, 

 distantibus, erosis. Long. 40, lat. 33 mm. 



