38 AMPHITHERIID &. 
These jaws have the coarse fibrous structure, and dark 
glistening surface from the abundant proportion of animal 
matter common in fossil cold-blooded Vertebrata, and their 
composite structure is obvious, from the distinct deep 
fissure extending along their base between the dental and 
opercular pieces; the articulated pieces of these compound 
jaws more or less resemble the coronoid, condyloid, and 
angular, processes of carnivorous Mammalia, as they do 
also in most osseous fishes, but most distinctly in Reptiles, 
where the detached elements of the Jaw are more numerous. 
The teeth are often black, glistening and bituminous from 
their abundance of animal matter and carbon, as in most 
fossil fishes ; their crowns are compressed, free, multicuspid, 
and their cervix much contracted and long, as in the 
Amboyna lizard, the iguana, iguanodon, many fishes, Xe., 
and their surface is minutely furrowed with close vertical 
grooves near their cervix, as in most Saurian reptiles and 
Sauroid fishes. The fangs are deeply implanted in the jaw, 
as in all the Acanthuri, &c., and they are bifid, as in 
many Squali, and in the closely allied Basilosaurus. At 
least eleven similar multicuspid molars are seen in a frag- 
ment of one side of the lower jaw, as commonly observed 
in fishes and reptiles, but never in mammiferous quad- 
rupeds. 
‘“¢ | have examined four of these jaws in England which 
have been referred to didelphis; and the jaw at Paris, 
from the same locality as the others, is acknowledged 
by all to belong to a reptile, as demonstrated by Blain- 
ville. The supposed incisores, instead of being small, 
symmetrical, approximated, and parallel, as in insectivorous 
and carnivorous mammalia, are long, conical, irregular, 
widely separated from each other at their base, almost 
as long and large as the supposed canine, and diverging, 
