INVERTEBRATA. 405 



Some conception of the extent of this group of shells 

 may be formed, when the statement is made, that one of the 

 subgenera, Unio, has nearly four hundred species on the 

 continent of North America.* Many species of this sub- 

 genus are found in the fresh waters of the mountain slopes, 

 but they do not ascend to the highest runs near the summit. 



Subgenus Anodonta has forty -three North American 

 species, and subgenus Margaritana sixteen North Ameri- 

 can species. These have representatives in the mountain 

 streams. 



Family CYCLAD^E. 



CYCLAS, (Lam.) Dekay enumerates several species of 

 Cyclas as belonging to New York. The similis is found in 

 ponds and streams of every part of the State of New York, 

 also dubia. The Partumeia in swamps and sluggish streams, 

 also in every part of the State. He enumerates the rhom- 

 boides, elegans, and edentula. 



CLASS Y. BRACHIOPODA. 

 This class contains but few shells, all of which are marine. 



CLASS VI. CIRROPODA. 



This last division of the mollusks contains the smallest 

 number of species. They belong to the ocean. 



* These facts are taken from Mr. Lea's Synopsis, third edition, 

 1852. Since then he has described over one hundred species of 

 Unionidse indigenous to our country, and added greatly to the foreign 

 synonomy, all of which he will publish in the fourth edition, now in 

 preparation. 



