CHONETES OF THE CHEMUNG GROUP. 
145 
while its surface markings, when entire, consist of fine closely arranged striae, 
and in a partially exfoliated condition it is marked by two sets of excentric 
lines crossing each other, which give a very peculiar aspect; while the absence 
of spines upon the surface readily distinguishes it. 
I have seen that species' only from the beds below the Burlington limestone, at 
Burlington ; and we do not know what modifications may take place in its cha¬ 
racters in distant localities. 
The Chonetes muricata, in its truncate apex and spiniferous surface, has the 
external aspect of Strophalosia ; but a careful examination shows all the dis¬ 
tinctive features of Chonetes. A single specimen, partially preserving the shell 
on the hinge-line, shows an area on the ventral valve of nearly a line in width in 
the centre, the dorsal area being about one-third as wide. 
Geological formation and localities. In the arenaceous and semicalcareous beds 
of the Chemung group, at Ellington in Chautauqua county, New-York; and at 
Meadville, Pennsylvania. 
In addition to the species which are clearly recognised in the Chemung group, 
there are casts of the interior and impressions of the exterior of one or two 
others which cannot be satisfactorily referred to any known forms, and which 
are not in a condition to be described as distinct species. 
In the eastern part of Ohio there is a species of Chonetes occurring in beds 
from sixty to one hundred feet below the Carboniferous conglomerate, and in a 
position somewhat higher than the beds from which the principal part of the 
fossils in New-York are obtained, which bears a close resemblance if not identity 
with the C. illinoisensis. It occurs in association with C. logani, and is distinguished 
by its larger and more gibbous form and finely striated surface, having from 80 
to 120 fine subequal striae upon the surface of the ventral valve. When exfoliated, 
the surface is finely and regularly punctate between the striae. The cardinal 
margin bears three or four slender diverging spines on each side of the beak (not 
“ five or six oblique spines on each side of the beak,”) as in C. illinoisensis. 
Paleontology IY. 
19 
