776 



bus dentibus insequalibus arcuatis; sinu pallii magno, lato, basi 

 obliquissimo." 



Much less oblique than P. lithophaga, more square in front, 

 with the umboes flattened in the middle, free from ribs in front, 

 while in the middle the riblets have broad interstices, and at the 

 back are slightly crenulated. 



Chinese Seas. Cuming. 



17. Petricola semilamellata (pi. clxvi. f. 23), Lamarck, 

 An. s. vert. v. 503. no. 3. 



Pet. testa alba, tenui, oblique subglobosa, postice paululum at- 

 tenuata, sulcis concentricis minutis irregularibus, postice subla- 

 mellosis. 



A hght, obliquely globose, small shell, shaped something hke 

 P. litliopliaga, but with no longitudinal ridges, and very fine con- 

 centric ridges, which are lamellated at the back. 



Eochelle. 



18. Petricola bicoloe (pi. clxvi. f. 22), Sowerly , jim. 

 Pet. testa ovata, tenui, radiatim minute striata utrinque hiante, 



antice rotundata brevi postice oblique subattenuata macula fusca 

 trigona pallida. 



An inflated shell, belonging to the same group with P. IHlio- 

 phaga, but equally and finely striated, gaping at both ends, with 

 a triangular patch of pale brown at the back. 



Mr. Hanley^s collection. 



19. Petricola divaricata (pi. clxvi. f. 24, 25), Chemnitz, 

 Conch, pi. 172. f. 1666, 1667. Narinio divaricata. Gray. 



Pet. testa solida, oblique subquadrata, alba, intus lutescente, om- 

 nino divaricatim striata, antice brevissima, umbonibus prominenti- 

 bus terminahbus, postice truncata margine foliata incrassata. 



Solid, rather obliquely squarish, white, yellowish within, all over 

 striated in sharp angles; front side short, with the apex quite 

 terminal ;• hinder side oblong, truncated, with the edge thickened 

 and foliated. 



Deshayes gives as localities Indian Ocean and New Holland. 

 Mr. Cuming's specimen is marked " Red Sea." 



20. Petricola lapicida (pi. clxvi. f. 26), Chemnitz, Conch, 

 pi. 172. f. 1664, 1665. Narinio costata. Gray. 



Pet. testa P. divaricata simili, sed striis divaricatis evanidis, 

 postice costellis validis subdistantibus radiata. 



