22 MAZATLAN BIVALVES 



S. Elena, D'OrUgny. Panama, common, C. B. Adams. 

 Mazatlan ; extremely rare ; f'pool Col. 

 Tablet 75 contains 1 specimen, laid open. 



31. CORBULA BIEADIATA, Sow. 



Proc. Zool. Soc. 1833, p. 35 Mull. Syn. Test. Viv. p. 230. 

 Eve. Conch. Ic. pi. 1, f. 3. Hani. Suppl. Wood's Ind. Test. 

 pi. 10. f. 51. Hani. Descr. Cat. p. 47. .5. M. Cat. D'Orb. 

 Moll. p. 70. no. 620. 



Shell with valves nearly equal, ventral margin flattened, 

 posteriorly rather widely overlapping. Epidermis scarcely 

 visible except at the margin, where it is, as usual, thick. Within, 

 purplish white, ligament attached to larger tooth. Posterior 

 muscular scar strongly marked, partly projecting, partly indent- 

 ed, subcircular, with the little one behind coalescent. Anterior 

 scar pear-shaped. Pallial line irregular ; sinus very small. 

 Long. '33, lot. *52, alt. '26. 



Hob. Mud and sand, 3-6 fms., Chiriqui : 7 fm., in Bay of Carac- 

 cas: Cuming. Ecuador; Chiriqui: IfOrbigny. W. Columbia, 

 Jay. Panama, very rare, C. B. Adams. Grulf of California, 

 Mus. Cuming. Mazatlan ; extremely rare : L'pool Col. 

 Tablet 76 contains the only specimen found, in extremely 

 fine condition, flattened. 



32. COEBTJLA PUSTULOSA, n. S. 



C. t. parvd, alba, obesd, solidd, postice productd, truncatd, 

 antice rotundatd, ab umbonibus postice subangulatd ; valvd 

 minore plus minusve inclausd, maxime in margine ventrali ad 

 posticwm decurrente, arcuata : valvis concentrice liratis, liris 

 irregularibus, subrotundatis : epidermide tenui, ad marginem 

 crassd : lin'eis exillimis radiantibns pustular urn 

 minim arum repletis : umbonibus Icevigatis. 



Shell small, white, subglobose, produced posteriorly, with 

 the valves overlapping, bent at the posterior end of the ventral 

 margin ; with irregular, somewhat rounded concentric ridges, 

 crossed by the finest radiating lines, which under the microscope 

 are found to consist of rows of minute pustules, probably 

 formed in the epidermis, which is extremely thin over the body 

 of the shell, coarse round the margin, and at the posterior side, 

 which is rather angulated. 



Mr. Cuming's specimen measures long. '16, lat. "24, alt. "14, 

 The Mazatlan specimen '11, '16, "11. 



