87 
been put fully in possession of the rules and the leading examples 
which apply to such cases. And hence it will not I trust be deemed 
presumptuous, if, without pretending to any power of deciding a 
question of zoology, I venture to state the result of these discus- 
sions. It appears, then, that some of the marks by which the under 
jaws of Mammals are distinguished from those of Saurians are the 
following : (1) a convex condyle ; (2) a broad and generally elevated 
coronoid process, (3) rising near the condyle; (4) the jaw in one 
piece ; (5) the teeth multicuspid, and (6) of varied forms, (7) with 
double fangs, (§) inserted in distinct sockets, but (9) loose and not 
anchylosed with thejaw. In all these respects the Saurians differ ; ha- 
ving, for instance, instead of a simple jaw, one composed of six bones 
with peculiar forms and relations, and marked by Cuvier with di- 
stinct names; having the teeth with an expanded and simple fang, or 
anchylosed in a groove, and so on. Of course, it will be supposed, 
by any one acquainted with the usual character of natural groups, 
that this line of distinction will not be quite sharp and unbroken, 
but that there will be apparent transgressions of the rule, while yet 
the unity of the group is indubitable, Thus the Indian Monitor 
and the Iguana, though Saurians, violate the second character, 
having an elevated coronoid process ; but then it is narrow, and this 
seeming defect in our second character is further remedied by 
the third; forin those Saurians there is a depressed space between 
the condyle and the coronoid process quite different from that which 
a mammal jaw exhibits. Again, the teeth of Crocodiles, Plesio- 
saurs, and the like, are inserted in distinct sockets; but then they 
have not double fangs. The Basilosaurus was supposed to be a sau- 
rian with double-fanged teeth, but that exception was disposed of 
afterwards. And as there are thus saurians which trench upon the 
characters of mammals, there are mammals in which some of the 
above characters are wanting: thus the condyle is slightly or not 
at all convex in the Ruminantia ; there is no elevated coronoid pro- 
cess in the EKdentata; the Dolphin and Porpoise have not multi- 
cuspid teeth; the Armadillo has not varied forms of teeth, nor has 
it double fangs to its teeth, which also the fossil Megatherium has 
not. Still, upon the whole, the above appears to be the general 
line of distinction. Even if one or two of the above nine marks 
were wanting to prove the animal a mammal, still if the great ma- _ 
