232 DR. MORTON'S OBSERVATIONS ON 



at the time that Cuvier had already given this specific designation to a fossil species. 

 It therefore becomes necessary to change it, which I do by placing this species in 

 the zoological system by the name of 



HIPPOPOTAMUS (TETRAPROTODON) LIBERIENSIS. 



The Little or Liberian Hippopotamus. 



Dental Formula. 



4 2—2 



Incisors, — or, 



2 1—1 



Canines, 



1—1 



4—4. 



False molars, 



4—4 



3—3 



Molars, 



3—3 



Of the two skulls in my possession, one is that of a very old individual, in which 

 the teeth are much worn down, and the incisors, canines, and two first false molars 

 on each have been lost. This head is entire, excepting a small part of the nasal and 

 maxillary bones of one side. The lower jaw is wanting. PI. 34, fig. 5. 



The other head is of the same size and proportions, but has pertained to a younger 

 animal. It retains all the teeth, and for this reason I have used it exclusively in the 

 following dental observations. It also retains the lower jaw ; but the occiput, 

 orbit and zygomse have been fractured, and parts of the bones lost. There are also 

 three slug or bullet wounds through the nasal region. PI. 32. 



Upper Jaw. — The central incisors are slightly flattened, and about a quarter of an 

 inch in diameter at the alveolar margin. The lateral incisors are less flattened and more 

 conical. All these teeth are slightly curved and nearly vertical. PI. 34, fig. 3, 

 and plate 33, fig. 3. 



The canines are about an inch in the longest diameter, and remarkable for a 

 deep posterior groove or furrow, extending about half the depth of the tooth, and 

 giving its cross section (and consequently the corresponding alveolus) a reniform 

 outline. PI. 34, fig. 2. These teeth are much worn by attrition. 



False molars. — The first of this set is little more than an inch in length, slightly 

 curved, and has but a single fang and point. PI. 33, fig. 5. The second and third 

 false molars are very much larger than the first, with two fangs. They run to an 

 irregular conical point, with a second rudimentary point on the posterior margin. 

 The fourth false molar is less in size than the second and third, and is only partially 



