487 



5. Pholas costata (pi. cii. f. 8^ 9), Linn. 1111. 



Ph. testa aperta, elongata, veiitricosa; costis validis subrotuu- 

 datis, imbricatis, omniiio radiata ; lamina dorsali triangulari, 

 cornea. 



Ventricose, with thick, imbricated ribs radiating over the whole 

 shell. The dorsal shield is broad,, triangular, horny, with a cen- 

 tral apex, placed upon a triangular disc, formed by the reflection 

 of the dorsal edge of the shell over the umbones. 



Collected in rocks at Mexico, and United States, America. 



6. Pholas parva (pi. civ. f. 31, 32), Pennant. 



Ph. testa aperta, ventricosa, antice emarginata, angulari ; costis 

 radiatis et lineis concentricis cancellata; ad marginem dorsalem 

 reliexa ; lamina dorsali angustata, apice postica. 



Open, ventricose, gaping angularly in front, with the umbones 

 nearly central, shielded by a narrow curved plate placed on the 

 reflected margins of the dorsal edge. 



Pound in many ports of Great Britain. 



7. Pholas Manilla (pi. ciii. f. 17, 18), Sowerhy, junr., 

 Pro. Zool. Soc, 1849. 



Ph. testa aperta, elongata, antice subangulata ; costis subdis- 

 tantibus, acutissime imbricatis, omninb radiata; umbonibus sub- 

 anticis ; ad marginem dorsalem, ante umbones, area plana ; lamina 

 dorsali parva, arcuata. 



Much longer and narrower than Ph. similis, with the dorsal 

 shield much smaller in proportion. 



Prom Manilla bay. Cuming. 



8. Pholas similis (pi. ciii. f. 12, 13, 14), Grai/, MS. Brit. 

 Museum. 



Ph. testa late aperta, ventricosa, tenui, antice acute angulata, 

 postice subattenuata ; costis distantibus, angulatis, acute imbri- 

 catis, antice radiata ; umbonibus subcentralibus ; ad marginem 

 dorsalem, ante umbones, area plana ; lamina dorsali magna, arcuata, 

 apice terminali. 



A rather ventricose shell, angular at the anterior extremity, 

 and very widely gaping at the ventral margin. The ribs are few, 

 sharply imbricated, and spreading over the anterior part of the 

 shell only. The umbones are nearer the centre than in Ph. 

 Manilloi, and the dorsal shield is much larger in proportion. 



Prom New Zealand. Earle. 



3 R 2 



