yew Specimen of Cladodus clarki. — Claupole. 3 
somewhat abnormal genera. It had, however, the same down- 
ward look as if indicating a habit of feeding upon the ground. 
The Jail's. The jaws, though much crushed, can be readily 
traced in spite of some amount of displacement. By the as- 
sistance of some other specimens of the same and kindred 
species, we are able without much difficulty to trace the out- 
lines so far as they are preserved. The maxillaries project 
strongly at the sides of the head and give it its great width 
at that part. Within them lie the mandibles. The former 
are much curved in outline, the latter are more nearly straight. 
The condj^les are fairly well preserved, especially that on the 
right side. They have very nearly the same form as was 
shown in the figure of Cladodus inagniflciis, the description 
of which appeared in the September number of the American 
Geologist. They consist of wide flat plates of ossified carti- 
lage, corrugated as there shown and having a similar arrange- 
ment for the accommodation of the files of teeth. 
The Teeth. But the most valuable contribution to our 
knowledge which this fossil alfords is undoubtedly, as said 
above, that derived from the teeth, which are admirably pre- 
served and have been carefully exposed by the discoverer. 
Both their number and position can be determined with a re- 
markable degree of minuteness and accuracy. In fact, this 
single specimen places our knowledge of the dentition of the 
cladodont sharksin a completely new and satisfactory position. 
The upper jaw on the left side of the fish is in tlie best con- 
dition, though the anterior portion is separated from the rest, 
which lies well exposed to view. On the latter part are eleven 
files of cladodent teeth in succession and nearly equidistant 
from one another. These teeth are all alike in form but differ 
somewhat in size, those of the anterior files being rather the 
largest. In the second file from the front at least seven teeth 
can be counted, and there are indistinct traces of one or two 
more. The next two are less distinct in consequence of the 
fracture of the stone, which is unfortunately broken slant- 
ingly across the head along the dotted line shown in the fig- 
ure, and the fractured surfaces were much weathered when it 
was found, so that it is not now possible to restore the details 
over the area left blank behind the line of fracture. But on 
several files farther back in the mouth seven teeth can agaiu 
