1040 On the genus Hexaprotodon. [Dec. 



establish the sub -genus as a new group, of which, they describe two 

 species. In these animals the incisors are not only different in number 

 from those of Hippopotami, but are also more uniformly develop- 

 ed, and are prolonged almost straight forward in the long axis 

 of the head, the general proportions of which, though considerably 

 less than those of the existing hippopotamus, are proportionably more 

 massive and ponderous, while the incisors on the contrary are 

 more slender, so much so as to preclude the supposition that they 

 could have been used either for digging up roots, or as an arma- 

 ture in committing those violent depredations on dry land ascribed to 

 the hippopotamus. It is therefore probable, as has been observed, that 

 their habits were more aquatic. What proportion the head bore to the 

 body we have as yet no means of knowing, the vertebrae and bones of 

 the extremities not being yet determined, but we may still attain a far- 

 ther insight into the characters of the Hexaprotodons by comparing such 

 fragments of their jaws as have been found with the corresponding 

 parts of the existing hippopotamus, and we find by this means that 

 although the length of the jaws from the alveolus of the incisors to the 

 last molar is, 9-| inches in the latter, and from 11^ to 13 inches in 

 several specimens of the former, yet that the thickness or depth of the 

 lower jaw at the symphysis is only four inches in the existing hippo- 

 potamus, while this measurement amounts to 5-| inches in some of the 

 hexaprotodons. In the first the breadth of the jaw at the narrowest 

 part behind the canine teeth is five inches, and in one of the latter 

 species, six ; thus indicating a weight and massiveness in the head of the 

 hexaprotodon which if attended with corresponding proportions in other 

 parts of the frame must have belonged to an animal almost too unwieldy 

 for locomotion on dry land, the hippopotamus itself from the shortness 

 of its limbs being barely capable of such a mode of progression. The 

 ponderous character of the jaws of the Hexaprotodons also implies a 

 proportionably powerful muscular system ; and when we contrast such a 

 condition with the slender size of the incisors which are extended forward 

 like a grate of comparatively long delicate bars, we can conceive no other 

 object of such a structure than that of raking the Fuel and Confervoid 

 plants either from the surface of water or from sands or soft muddy 

 banks of rivers or lakes. Whether such will eventually prove to have 

 been the case or not, will depend on the success that may attend the 

 researches of zoologists in identifying other parts of the skeletons of 

 this interesting group, in addition to those fragments that have already 

 been identified by Dr. Falconer and Captain Cautley. At present 

 we can only be guided by the facts that are laid before us, and perhaps 





