OF CONCHOLOGY. 65 



widening from the top, which is nar- 

 row and pointed, to the base which is 

 wide and extended. 



In Turton's Linne eighteen species 

 of Pinnee are described ; and three 

 only have been found to inhabit the 

 British seas. 



ORDER THIRD. 



UNIVALVE SHELLS 



With a regular Spire. 



Genusl8th -ARGONAUTA. Ani- 

 mal a Sepia or Clio ; shell univalve, 

 spiral, involute, membranaceous, and 

 unilocular, or consisting of a single 

 apartment or cell. IAnn St/st. 317. 

 Plate 7th, fig. 18th. 



Habitation. The Argonautae have 



onlv been found to inhabit the ocean, 

 K 



