MOLLUSC A OR UNIVALVES. 269 



whorls contiguous and apparent ; partitions 

 sinuous ; mouth round. — 1 species, fossil. 



133. Baculites. — Shell straight, cylin- 

 drical, sometimes slightly compressed, and 



somewhat conical ; partitions sinuous, trans- 

 verse, a little distant. — 3 species. 



All fossil; abundant in the limestone of Va- 

 lognes in Normandy. 



Division II. — Monothalama.* 



134. Argonaut a. — Shell monothalamous, 

 symmetrical, external, and containing, (but not 



* Monothalames, Lamarck. 



