Bihliographical Notices. 67 



is found in that species having the second costa of the molar teeth 

 more prominent, in the anterior collis having no vertical groove 

 on its posterior side, in the ante-crotchet of u±. Blanfordi being 

 absent, while the crotchet is relatively larger. The molar teeth of 

 Aceraiherium perime'iise are distinguished from those of A. Blanfordi 

 by greater development of the buttress and costa, while the ante- 

 crotchet is less developed, and the posterior valley forms a deep pit 

 instead of a slit. Figures are given of the mandible, showing its 

 general form, and indicating that the symphysis approximated to 

 the characters of the Javan rhinoceros. 



The lower molars have a faint trace of an external cingulum. 

 After comparing this Indian fossil with other species of rhinoceros, 

 the author concludes that there is a strong presumption that it is 

 an Acerallierium, though it is difficult at present to establish distinc- 

 tion from its American allies. The two races are distinguished 

 as majus and minus. Among European types it finds its nearest 

 ally in A. incisivum ; and the Rhinoceros deccanensis is thought to 

 have been a descendant from the same stock as Aceratherium Blan- 

 fordi. 



Hipparion antilopinum has a cranium referred to it from the 

 Siwaliks of Perim Island, in which the teeth exhibit the com- 

 plete isolation of the anterior pillar characteristic of Hipparion, 

 though the pillar is less elongated than in the teeth referred to H. 

 Tlieobaldi. Still, the skull is only determined provisionally, and is 

 compared with H. gracile, with the conclusion that the form of the 

 posterior maxillary cavity establishes a specific distinction. Other 

 teeth from Perim Island are described, and if they prove to belong 

 to a new species it may be named H. Feddeni. 



The remainder of the memoir is devoted to Mastodons. Three 

 tretalophodont species and two trilophodont species have been 

 already described from the Siwaliks, and the author now indi- 

 cates trilophodont types. Concerning the genealogy of the 

 Elephants, it is observed that the presence of simple tetraconodonfc 

 premolars in some Mastodons suggests their descent from some 

 ungulate with teeth of this type, in which premolars were as fully 

 developed as molars ; and that it is merely necessary to assume 

 the addition of an extra pair of columns in each of the true 

 molars of the Bunodont Artiodactyla to produce a dentition analo- 

 gous to that of the simple- toothed Mastodons. A variety of Mas- 

 todon angustidens naraed M. palceindicus is described from teeth. 

 It has a tendency to a rather more complex structure of the molars 

 than is usual in the European type, and there is a greater curvature 

 of the borders of the crown in the third molar of the lower jaw, 

 both these characters approximating towards M. pandionis, with 

 which it is associated in the extreme western border of India. 

 Further descriptions are given of teeth of Mastodon pandionis, which 

 is also closely allied to Mastodon angustidens, though the structure 

 of the molars is more complex and the cement of the teeth is deve- 

 loped. It appears to have survived to a later epoch than M. 

 angustidens, being found in the Upper Siwaliks. 



