HIPPOPOTAMUS. 565 



marinis,' tab. xii, fig. 1, (1747) the notches extend to the summits of 

 these ridges. I have given an original figure (PI. 142, fig. 3) of one 

 of these problematical teeth, from the specimen which now forms 

 part of the Woodwardian Collection at Cambridge, by the kind 

 permission of the eloquent Professor of Geology in that University ; 

 the anterior border is not so regularly notched as in Scilla's figure ; 

 and the two fangs shew the moderate proportions of those of the 

 premolars of the Hippopotamus, and by no means the ventricose 

 character of the roots of the teeth of a seal, to which family of 

 Carnivora this ancient fossil has been referred (2). 



The true molars are primarily divided into two lobes or cones 

 by a wide transverse valley, and each lobe is subdivided by a narrow 

 antero-posterior cleft into two half cones, with their flat sides next 

 each other; the convex side of each half cone is indented by two 

 angular vertical notches, bounding a strong intermediate prominence, 

 the analogue of that which rises out of the outer depression of the 

 Ruminant's molar (PL 134, fig. 3, o o) : a strong ridge bounds the 

 fore and the back part of the base of the crown and extends 

 completely round the last upper molar. A view of the unworn 

 summits of the crown of a true molar of the Hippopotamus is given 

 in PL 143, fig. 3. When these summits begin to be abraded each 

 lobe or pair of demi-cones presents a double trefoil of enamel on the 

 grinding surface : when attrition has proceeded to the base of the 

 half cones, then the grinding surface of each lobe presents a 

 quadrilobate figure, as shown in PL 143, fig. 4. The crown of the 

 last molar tooth of the lower jaw is lengthened out by a fifth cone, 

 developed behind the two normal pairs of half cones, and smaller 

 in all its dimensions. The enamel on all the molars of the 

 Hippopotamus is thick and has a wrinkled and punctate exterior. 

 The three last persistent premolars have each two fangs in both jaws. 

 The true molars have four fangs, except the last below, which has five. 



Extinct Hippopotamida. — The fossil Hippopotamus major adheres 

 closely to the type of the dentition of the existing species, the most 

 marked distinction being the diastema between the second (first per- 



(2) It is the Phoca dubia melitensis of M. de Blainville, ' Osteographie de Phoca, 4to. p. 46 ; 

 apparently on the authority of M. Agassiz, p. 44. 



