162 



f*5hell large, delicate ; inferior margins well roundefl ; anterior 

 somewhat abrupt. Striations hardly visible, color dark olive 

 green. 



Remarks. The outline of this shell would render it similar to 

 the C. minor of Adams, but it is much more inflated, the beaks 

 are more prominent, and the color is also different. 



PisiDiuM FERRUGiNEUM. P. testa ovata, complanata, sub- 

 elongata, postice rotundata, tenuiter striata, umbonibus parvis, 

 elevatissimis, non approximatis. Long. 0.17 ; lat. 0.13 ; diam. 

 9.11 inches. Hah. Massachusetts. 



Shell elongated, inflated ; beaks very tumid, but small; mar- 

 gins abrupt ; color pale yellow. 



Remarks. This species is different from any other known ; 

 it is remarkable for the tumidity of the beaks, which neverthe- 

 less are very small and separate one 'from another. The spe- 

 cimens are generally found covered with a fine red mud, much 

 the color of oxide of iron. Found at Salem, and rarely at Cam- 

 bridge, in company with the C. securis Nobis. Cabinet of the 

 Boston Society of Natural History. 



PisiDiUM KuRTzii. P. testa minutissima, compressa, subequi- 

 laterali, postice rotundata, umbonibus magnis, elevatis, approxi- 

 matis. Long. 0.12 ; lat. 0.09 ; diam. 0.075 inches. Hab. South 

 Carolina. (Lieut. Kurtz.) 



Shell depressed, outline generally rounded, especially ante- 

 riorly; beaks very tumid and approximate ; color pale yellow. 



Remarks. This species somewhat resembles the C. minor 

 Adams, in outline, but is more equilateral, smaller, and more 

 depressed. 



PisiDiuM zoNATUM. P. tcsta magna, compressa, elongata, 

 inequilaterali, postice rotundata, umbonibus parvis, elevatis, non 

 approximatis. Long. 0.22 ; lat. 0.18 ; diam. 0.13 inches. Hah. 

 Massachusetts. 



Shell large, compressed, elongated, posteriorly rounded ; 

 beaks small but elevated ; color light yellow with zones of white. 



Remarks. The outline of this species is very like that of 

 the P. ohscurum Nobis, perhaps anteriorly, rather more rounded. 

 The P. ohscurum is nevertheless very different in its circumfe- 

 rence, which is very much more inflated, its beaks are likewise 



