GEOLOGICAL SOCIETY. 99 



which the terminals of the three first feet are fila- 

 mentous 5 by reference to fig 2. pi. v. it seems not im- 

 probable that these filaments exist on the under surface 

 of some of the other articulations, an appearance of 

 which is observed on one of the left extremities. 



A comparative view will display other distinctive 

 characters. Vid. pi. v. fig. i.; E. remipes, fig. ii.; E. 

 lacustris. 



Locality. Williamsville, seven miles below Buffalo. 

 Place in the Geological series* Grauwacke slate ? 



For the following list of the genera of North American 

 Trilobites, and synopsis of the species, the author ac- 

 knowledges himself indebted to the politeness of Dr. 

 Green, who has presented to geologists the very best 

 monograph on this subject, accompanied with beautiful 

 plaster casts of each species. 



Admitting the composition of the Grauwacke series 

 of rocks to be the same as that proposed by De la Beche, 

 all the crustaceous organic remains belong to this group. 

 The following list includes all the species of Trilobites 

 discovered in this country. 



Genus Calymene, Brongniart. 



C. Blumenbachii, Al. Brong. 



Localities. Lebanon, Ohio; Trenton Falls, New 

 York ; near Reading, Pennsylvania, and many other 

 places. No Trilobite is so extensively diffused over the 

 United States, as the C. Blumenbachii. See Green's 



