MAMMALIA. 431 
reminding us of those of the Hippopotamus. The remains of but che 
species, C. subapenninum, of this genus have been found in the tertiary 
deposits of Italy. 
A fossil genus Chirotherium has been established from some foot-prints, 
at first referred to the opossum family, and afterwards believed to be a 
gigantic batrachian animal. Although differently spelt, its etymology is the 
same as that of Cheirotherium, making two homonymous genera in the 
nomenclature, one in the class of Mammalia, another, still douktful, in the 
class of reptiles. The latter is probably identical with Labyrinthodon. 
The genus Cymathotherium is placed among Sirenidia, perhaps with no 
propriety. The only part which we possess of that animal is a fragment of 
the lower jaw. ‘This jaw seems to bear but one single developed tooth, a 
little elevated above the margin of the bone. The crown of the tooth itself 
is compressed, and its base dilated; the root is long, exteriorly curved; its 
surface is furrowed, and the inner side exhibits a deep groove. C. antiquum 
is from the diluvial deposits of Germany. Its size, we are told, reached that 
of the Dugong. 
The genus Zoxodon bears a great resemblance to pachyderms, and will 
undoubtedly prove to be a-synthetic type of the latter and Sirenidia. Its 
real affinities, however, are not understood, inasmuch as great diversity of 
opinion exists among naturalists on their account. It is compared alter- 
nately with Rodentia, Cetacea, Edentata, and Pachydermata. By some it 
is brought near the seals; by others near the pachyderms, which it 
resembles most in the structure of its teeth. Now, if Toxodon approxi- 
mates to pachyderms, and was constructed to lead an aquatic life, it 
must enter the group of Sirenidia. Toxodon had no canines; trenchant 
incisors. The molars recall to the mind those of Kdentata; they are seven 
in number on each side, and implanted in the jaws with the convexity out- 
wards. [ 
The only well ascertained species of this genus was found at Bahia 
Blanca, on the banks of the Rio Negro (South America). Another, but 
doubtful species, is established upon a humeral bone found in Colombia 
(South America). 
Fam. 2. Manatip#. In the genus MJanatus, the grinding teeth are more 
numerous than in the others of the same family, being eight in number. 
The crown of these is square and flat, marked with transverse ridges, and 
provided with a root distinct from the crown. The incisors are in a 
rudimentary state in the young; the canines constantly wanting. The 
pectoral fins exhibit on their edge the tips of four nails. The caudal fin is 
rounded. The species hitherto known in a recent state are few in number, 
and seem to differ but little from each other. JL americanus or australis 
is found on the Atlantic coast of South America, from which it ascends 
into the rivers, especially the Amazon and tributaries. JZ. senegalensis is 
another, from the western coast of Africa. This species is smaller than 
that of America, being seldom more than about eight feet long. Its color is 
blackish ash. A third but doubtful species, MZ. latirostris, is said to be pecu- 
har to East Florida, the Gulf of Mexico, and perhaps the West Indian seas. 
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