412 ON THB FOSSIL BONES OF PACHYDERMATOUS QUADRUPEDS. 



the incisors. It is also broken above, so as to give but a very imperfect 

 view of the curvity terminating at the symphysis. 



The dimensions of these two entire teeth, and of ail the parts of this 

 jaw, which may be determined with accuracy, are such as to leave no 

 room for doubting of their belonging to an hippopotamus of a much 

 smaller species than that of our times. 



The last molar is 0,03 long. In a living hippopotamus of ordinary 

 size it is 0,064 ; and in the fossil jaw of our Museum, 0,085. This 

 last dimension is almost triple. The penultimate is 0,028 long ; in 

 the living hippopotamus it is 0,058 ; in the fossil it is not sufficiently 

 entire to admit of accurate measurement. 



Taking the bases of the three teeth we have 0.,07 : in the living we 

 find 0,17. 



Besides their smallness, these teeth have characters derived from 

 their formation : — 



1st. They have no collar or prominent border round their base. 



2nd. The discs of their crowns do not represent trefoil figures so 

 distinct as those of the hippopotamus ; they are more like lobes, 

 broad on the outside and a little slanted, than like trefoil figures. 



3rd. The last has not so longitudinal and so simple a fang as the last 

 tooth of the common hippopotamus, but merely three tuberosities, 

 forming a transverse fang, as in the penultimate. 



These pieces do not greatly exceed in size the corresponding pieces 

 of the small hippopotamus ; but as they do not bear a greater resem- 

 blance to them than to those of the large hippopotamus, no doubt can 

 be entertained of their constituting a particular species, and their re- 

 lations with the hippopotamus are quite strong enough to warrant us 

 in referring their species to that genus. 



Nevertheless we cannot look upon this assertion as demonstrated, 

 until we shall have been fortunate enough to find the canines and in- 

 cisors of this species*. 



Article IV. 



On some Teeth which indicate a Species allied to the Hippopotamus, and 

 Smaller than the Pig. 



These have been found with the teeth of crocodiles, twenty feet 

 deep, in a calcareous bank near Blaye, in the department of Charente. 

 I am indebted for them to M. Jouannet of Bourdeaux. 



Two of these (plate 38, figs. 12 to 17) present a well defined trefoil 

 figure on one side, although worn very low. 



A third (figs. 18 to 20), worn lower still, presents two figures with 

 four lobes. 



* M. Cristol, of Montpellier, having discovered a jaw of this fossil species, has 

 ascertained that it could not have belonged to an hippopotamus, and that its shape 

 seemed to claim an affinity with the trichecus dugoug, from which however it dif- 

 fered in the shape of its teeth. Hence we may conclude that this middle sized hip- 

 popotamus does in reality fpresent the characters of a new genus, approximating 

 perhaps to the trichecus dugong. 



