42 Bulletin 5 313 



136 FOSSIL SHELLS. 



striated like the general surface : within simple, 

 margin striated. 



Length four inches ; breadth rather more. 



This is a very fine shell, comparable with the 

 magellanica ; but the sides below the auricles 

 decline much more rapidly towards the base, and 

 the striae, judging from Bruguiere's figure, are 

 much more prominent and distinct. 



4. P. septenaruis. PI. ix. fig. 3. Shell convex, 

 suborbicular : atcricles subequal : surface with nu- 

 merous slightly scaly strise, and about seven re- 

 mote ribs, of which the three intermediate ones 

 are much elevated, rounded, or slightly flattened 

 on the top. 



Length nearly two inches and seven-tenths. 



But a single imperfect, inferior valve, occurs in 

 Mr. Finch's collection ; but this is so perfectly 

 distinct from any other that I have seen described, 

 that I have no hesitation to describe it as new. 

 The striae are equally distinct on the ribs, and in 

 the intermediate spaces. The scales are rather 

 thick, very small, and not confined to the striae, 

 but are also observable in the spaces between the 

 strise. 



PLICATULA. 



P. marginata. PI. ix. fig. 4. a. External view, 

 b. Internal view. Shell ovate-cuneiform, some- 

 what arcuated at base ; with about three much 



[J. A. N. S., Phila., ist Sen, Vol. IV, 1824.] 



