92 CONCHOLOGY. 



CLASS IV. 



MOLLUSC A. 



T W E N T Y-T WO FAMILIES. 



FAMILY I. 



Pteropoda. Six genera 



Some genera of this family are without a testaceous cov- 

 ering, and are mentioned only for the sake of preserving the 

 family entire. 



1. Hyalsea. Venus's Chariot. Two species. 

 This genus derives its common name from a fancied re- 

 semblance to a miniature triumphal car. 



Shell very thin, transparent, symmetrical, convex below, 

 flat above, valves unequal, form tricuspidated, cleft at the 

 sides, open like a cleft anteriorly, and tridentated posteri- 

 orly ; summit truncated. 



Hyalaea tridentata. Hyalasa cuspidata. 



H. tridentata. The three-toothed Hyalaea. 



Transparent, horn-coloured, globular; tridentated poste- 

 riorly ; summit and two posterior sides open ; finely striated 

 transversely. 



2. Clio. Has no Shell. Two species. 

 Clio Borealis. Clio Austrahs. 



3. Cleodora. Two species. 

 Shell gelatinous, cartilaginous, transparent, in shape of a 

 reversed pyramid or lanceolate truncated, only open at the 

 summit. 



Cleodora pyramidata. Cleodora caudata. 



