DESCRIPTION OF PLATES. 81 



shows three molars and three premolars, with a portion of the canine. 

 The condyle, coronoid process, and descending process are wanting. 

 The lower margin is straight. — B.M. 



Figs. 5 and 5 a. — H. Sivalensis. Lower jaw, more perfect ; viewed 

 from above and also laterally. The alveolar ridges on both sides are 

 perfect, and comprise three molars and three premolars, and also the 

 alveolus of a fourth premolar. Both canines are broken off; but the 

 right one is tolei - ably perfect, and is seen to curve back slightly at its 

 tip. The incisive ridge is perfect, but the teeth are wanting. The 

 width across the muzzle, from the outer side of one canine alveolus to 

 that of the other is greater, and the width of the jaAV over the penulti- 

 mate false molar is less, than in H. amphibius. The condyle, coronoid 

 process, and descending ramus are wanting. The lower margin is 

 straight. — B.M. 



Figs. 6 and 6 a. — H. Sivalensis. Lower jaw, viewed from above and 

 also laterally. The posterior molars on both sides are wanting; but 

 the two anterior molars and three premolars, on either side, and the two 

 canines and six incisors are present. The space between the anterior 

 premolar and the canine is very contracted. The right canine is very 

 perfect. The anterior angle of the jaw beloAv the canines is more 

 abrupt, and the depth of the body of the jaw more regular, than in II. 

 amphibius. The coronoid process is present, but the condyle and 

 descending portion are wanting. The coronoid process is not projected 

 so much forward as in //. amphibius. 



Figs. 7 and 7 a. — H. Sivalensis. Fragment showing symphysis of 

 lower jaw, with canines and incisors remarkably perfect. The hori- 

 zontal direction of the six incisors and the peculiar curve of the canines 

 upwards and slightly backwards are well seen. The incisors are of nearly 

 equal dimensions, and the two central ones are not larger, as in H. 

 amphibius ; they are cylindrical, and inclined outwards at an obtuse 

 angle to the plane of the grinding surface ; their ends are truncated. 

 They are much larger than in the specimen shown in fig. 6, so that the 

 animal was probably an adult male. — B.M. 



Fig. 8. — H. Sivalensis. Large descending process of ramus of lower 

 jaw, detached. This remarkable appendage for the attachment of the 

 masseter and temporal muscles, peculiar to the genus, is even more 

 developed than in II. amphibius ; it is less tapering and more deep and 

 massive in its proportions ; the posterior margin is more round, and 

 the anterior, w T hich in H. amphibius is curved and pointed forwards, is 

 here blunt and unmarked by any peculiarity of form. The process is 

 inclined outwards, and its outer surface is as marked for the reception 

 of muscles as in the living Hippopotamus. — B.M. 



Fig. 9. — II. Sivalensis. Another specimen of descending process of 

 ramus of lower jaw. 



Fig. 10. — Anterior portion of palate, with six incisors, and with 

 three premolars on right side, and two on left. — B.M. 



Figs. 11 and 11 a. — Anterior portion of palate with canine and two 

 premolars ; viewed from above, and also laterally. — B.M. 



