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 allied 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. 
24 
