MAMMALIA. 431 



reminding us of tliose of the Hippopotamus. Tlie remains of but one 

 species, G. suhopenninum^ 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 sjDclt, its etymology is the 

 same as that of Oheirotherium, making two homonymous genera in the 

 nomenclature, one in the class of Mammalia, another, still doubtful, in the 

 class of reptiles. The latter is probably identical with Labyrinthodon. 



The genus Gymathotherium is placed among Sirenidia, perhaps with no 

 propriet}^ 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. G. antiquum 

 is from the diluvial deposits of Germany. Its size, we are told, reached that 

 of the Dugong. 



The genus Toxodon 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 Eodentia, 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 Edentata ; 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. Manatid.E. In the genus Ilanatus, 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. II. americamis or australis 

 is found on the Atlantic coast of South America, from which it ascends 

 into the rivers, especially the Amazon and tributaries. J/, 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, M. latirostri's, is said to be pecu- 

 liar to East Florida, the Gulf of Mexico, ^nd perhaps the West Indian seas. 



635 



