CATSKILL GROUP. 



185 



The fossil which covers that part of the plant is a cast of a very common atrypa, left to show 

 its entombed associates. It appears to be more nearly aUied to Lepidodendron, than to any 

 of the other classes of fossil plants. 



There is a negative fact with respect to the third district which should be mentioned, and 

 that is the total disappearance of all the trilobites ; a fragment only of one was seen in this 

 rock. From the period of the deposit of the Genesee slate, they began rapidly to disappear ; 

 only three or four fragments, to my knowledge, having been found in any rock supposed to 

 be higher than the Tully limestone ; one of which, the head of an Asaphus (the bufo), was 

 found to the south of Ithaca at Bald hill ; another near Norwich, and the tail of the Dipleura 

 also at the latter locality. 



The following list presents all the fossils belonging to the Chemung group, which have 

 been identified and named by Mr. Conrad up to this time. 



Delthyris chemungensis. 



— prolata. 

 Strophomena mucronata. 



— lachrymosa. 



— lima. 



— chemungensis. 



— delthyris. 

 Avicula spinigera. 



Avicula protexta. 



— pectenoides. 



— multilineata. 



— chemungensis. 

 Cypricardites carinifera. 

 Inoceramus chemungensis. 

 Atrypa chemungensis. 



Geol. 3d Dist. 



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