52 NOTE ON THE FOSSIL HIPPOPOTAMUS 



As may be imagined in such an extensive collection we find the 

 remains of animals of all ages, with teeth in every variety and state of 

 detrition ; from the young animal with the complicated and triple 

 cylindered milk tooth, to the old and worn-down molar without any 

 mark of the trefoil, and with a simple encircling ridge of enamel. In 

 the fossil skull described as approaching adult (from which the measure- 

 ments noted as No. 1 . have been taken) we have a beautiful exhibition 

 of the teeth in that state when the animal has j ast lost its last milk tooth, 

 and the new molar or ' dent dc remplacement'' is just shewing itself in germ, 

 whilst the last permanent molar, or that most posterior, is in the same state 

 of advancement, having just pierced the bone : the oldest tooth in the head or 

 the first permanent molar is just worn to that state, when the development of 

 the trefoil crown is most perfect ; the second permanent molar is just shewing 

 this appearance on its two front pillars ; the front false or pointed molars are 

 unworn, and exhibit in all their perfection the richly embossed surface, 

 which is peculiar to these teeth in the Hippopotami. The first false molar 

 or milk tooth seems to have retained its position in many of our jGassils long 

 after the fall of the other milk teeth, and long after the arrival of the animal 

 at the adult state. In some of our skulls which are the remains of very old 

 animals, we observe the alveolus of this tooth very distinct, and having the 

 appearance more of having been broken off in the fossil, than of having been 

 lost previous to the death of the animal, in which case moreover a filling in of 

 the pit from the growth of the bone would be more or less evident in the 

 fossil. From the natural wear of the tusks upon each other, the truncated 

 extremity of the upper one, and in the Hippopotamus Sivalensis that which is 

 described as reniform, occurs on the convex or outer side of the tusk ; and this 

 must be the case wherever the tusk belongs to the upper j aw. Amongst a very 

 extensive and very large collection, containing as we before remarked three 

 perfect skulls, with a number of fragments of nearly perfect lower jaws, with 

 a great number of pieces of both more or less mutilated, the reniform tusk 

 is an invariable appendage to the upper, and the pyriform to the lower jaw. 



