42 AMPHITHERIID 4%. 
fangs diverge so immediately from the base of the crown, 
that this presents scarcely any contracted prolongation to 
which the term ‘ cervix’ can be properly applied; the con- 
trast between the teeth of the Amphitheriwm, and those of 
most Saurian Reptiles, is very striking in this respect. The 
enamelled surface of the teeth of the Amphitheriwm near 
the cervix is smooth and polished, and entirely devoid of 
any close vertical grooves. 
The bifid osseous base which supports the true dental 
tissues of the teeth of Squali cannot be adduced as a cor- 
responding structure to the two-fanged lower molars of the 
Amphitherium except by a forced and overstrained analogy ; 
the real bearing of the two-fanged structure of the teeth of 
the Amphitherium upon the question of its affinities, is kept 
out of sight by such a comparison; for it is the implan- 
tation of the teeth in deep double sockets of a bony jaw 
by the double fangs which demonstrates the mammalian 
character of the animal:* the bifid osseous base of the 
teeth of sharks is attached, as is well known, by ligaments, 
to a cartilaginous jaw. 
I was well aware, when replying to the objections of M. 
de Blainville, that portions of the jaws of a gigantic fossil 
Vertebrate animal, shewing teeth implanted by two fangs, 
had been discovered in the Alabama tertiary deposits, 
associated with Corbule, Modioli, sharks teeth, &c., and 
that these fossils had been referred by Dr. Harlan to a 
genus of Saurian Reptiles which he had called Basilo- 
saurus: but the very fact of the implantation of the teeth 
by double fangs—the first alleged example of such a structure 
in the Reptilian Class—led me to receive the ascription of 
* “¢'The teeth, composed of dense ivory with crowns covered with a thick coat 
of enamel, are every where distinct from the substance of the jaw, but have two 
fangs deeply imbedded in it.” Geol. Proceedings, Dec. 1838, p. 17. 
