AMPHITHERIUM. 3f 
as the front teeth of anarrhichas and many other fishes. 
There is a hinge-like, dentated appearance, consisting of 
three similar and equally distant grooves, as between the 
rami of the lower jaw of most osseous fishes, distinctly 
perceptible in Amphitherium Bucklandi, at the broken 
surface of the symphysis, and the lower jaw is arched, 
as in most fishes and Saurian reptiles. The coronoid, 
or complementary piece, is deeply concave interiorly, and 
its anterior suture is seen extending to the third posterior 
molar tooth, as in the Jguana. The condyloid, or arti- 
cular surface, passes obliquely into the imbedding hard 
rock, and may be concave, as in reptiles and fishes, but 
is not exposed. This animal has received its name from 
the mixed and ambiguous character of its relics, and the 
foot-marks of Chirotherium, left on the new red sandstone, 
have been referred to a similar didelphis existing at that 
early period. The great jaws, teeth, and vertebre of Basi- 
losaurus, approaching closely in its characters to Amphi- 
therium, were found in the oolite of the New World.” 
The high importance of the question touching the anti- 
quty of Mammalian organization calls for a due notice 
of the foregomg statements relative to the most  inte- 
resting fossils which have yet been discovered, and the 
more imperatively in this place, since they are peculiar 
to Great Britain, and, despite the numerous objections, 
are here admitted into the series of its fossil Mammalia. 
First, then, as to the alleged facts respecting these fossils of 
the Stonesfield Oolite, repeated scrutiny enables me to state, 
that, instead of presenting ‘the coarse fibrous structure’ com- 
mon in fossil cold-blooded Vertebrata, they have the pecu- 
liarly fine, compact structure which the jaws of insectivorous 
and marsupial Mammalia manifest. The alleged ‘ distinct, 
deep fissure, extending along their base, between the dental 
