BE PORT OF THE STATE GEOLOGIST. 



359 



Hamilton Group. 



Marcellus Shales. 

 The Trilobites found in these beds all pass upward into the 

 Hamilton shales where they attain a more complete development, 

 These are : 



Proetus Haldemani. 

 Proetus macrocephalus. 



Homalonotus Dekayi. 

 Phacops rana. 



Dalmanites (Cryphceus) Bouthi. 



The peculiar character of the sea which deposited these bitu- 

 minous shales was not favorable to the existence of these animals, 

 and it is only where the deposit becomes calcareous that the 

 trilobitic remains are found. In addition to these occurs the 

 earliest known species of the Devonian Phyllocarida, Mesothyra 

 (Dithyrocaris?) Veneris, and the interesting Cirripede, Protobalanus 

 Hamiltonensis. 



Hamilton Shales. 



In the rich fauna of these beds, the Crustacean element is much 

 more varied than at any other Devonian horizon. The Trilobites 

 have become much fewer in number since the close of the Upper 

 Helderberg period, the Crustacea being represented by other 

 orders of this class. The species occurring in the group are as 

 follows : 



Homalonotus Dekayi. 

 Phacops rana. 

 Phacops bufo. 

 Phacops Cacapona. 

 Dalmanites {Hausmannia ?)Meeki. 

 Dalmanites {Cryphceus) Pleione. 

 Dalmanites {Cryphceus) Boothi. 

 Dalmanites {Cryphceus) Boothi,\&i. 



Calliteles. 

 Dalmanites {Cryphceus) Barrisi. 

 Acidaspis Romingeri. 

 Proetus Haldemani. 

 Proetus macrocephalus. 



Proetus Rowi. 



Proetus jejunus. 



Proetus Phocion. 



Proetus Prouti. 



Proetus Nevada? . 



Proetus occidens. 



Proetus (?) longicauclus. 



Phaelionides gemmceus. 



Phaehonides (?) denticulatus. 



Cypjhaspis ornata. 



CypJtaspis ornata, var. baccata. 



Cyphaspis craspedota. 



Of this list those bearing a star (*) are from localities outside the 

 State of New York, which may be regarded as of the age of the 

 Hamilton group. 



Of the Phyllocarida, are : 



Echinocaris punctata. Mesothyra spumcea. 



Elymocaris capsella. {Dithyrocaris) Belli. 



Tropidocaris Hnmiltonice. Rhinocaris columbina. 



Mesothyra Neptuni. Rhinocaris scaphoptera. 



