MOLAR TEETH AND OTHER REMAINS OF MAMMALIA. 
53 
Attock. The specimen is from the right side of the upper jaw, and is either the second 
or third true molar. The crown of the tooth is nearly square ; the summits of the 
ridges are slightly abraded by oblique surfaces of wear, and there is a disc of 
pressure on both fore and hinder surfaces. 
The crown is raised into two parallel transverse ridges of nearly equal size ; 
these ridges are separated by a deep intervening valley, which extends completely 
across the tooth, and which slopes on the outer side quite down to the base, with- 
out any trace of a longitudinal wall connecting the two ridges. The posterior 
surfaces of the ridges are concave, and the anterior ridges slightly convex ; the worn 
surfaces on their summits slope towards the anterior extremity of the tooth. From 
the internal summit of the anterior ridge a wide ledge curves across the anterior 
surface of the tooth to the internal extremity of the ridge ; a smaller and nearly 
horizontal ledge joins the former at the antero-internal angle of the crown ; another 
waving and slightly cuspidate ledge, bounding a hollow, runs along the whole of the 
posterior surface of the tooth, and there is a small and blunted tubercle at both 
extremities of the median transverse valley ; these ledges and tubercles may be 
considered as an incomplete cingulum. The measurements of the specimen are as 
follows : — 
In. 
Length 
... 0-82 
Width of anterior surface 
... 
... 0-80 
Ditto of posterior ditto 
... 0-80 
The form of the tooth, as pointed out by H. von Meyer, differs from that of 
Tapirus and LopModon, in that the transverse valley extends completely across the 
crown, and that, consequently, the longitudinal outer wall connecting the transverse 
ridges of the molars of the latter genera is wanting. The teeth, were it not for 
their square form, might be mistaken for the lower molars of Tapirus ; they are of 
the simplest form of structure that occurs in any genus of this group of Mammalia. 
In certain upper molars of Lophiodon, figured by De Blainville {Osteographie Atlas 
vol. IV, plate Chceropotamus), the longitudinal outer wall is nearly absent, and the 
teeth ought, perhaps, to be referred to the present genus. 
The tooth differs from the upper molar of Listriodon from the Swiss Molasse, 
in that the ledges or cingula are not crenulated, and that the anterior of these is 
confined to the anterior surface, and does not extend round the outer extremity of 
the ridge to the median valley as in the European form. 
The upper molars of this genus resemble in form the upper molars of Dino~ 
therium, while those of Tapirus resemble the premolars of Dinotherium ; the latter 
genus is remarkable for having its premolars more complex than its molars ; the 
lower molars of Idstriodon are very like those of Tapirus. 
The teeth of this genus may be considered as transitional forms between the 
bunodont type of Tetraeondon (infra) and the lopJiodont type of Tapirus ; in the 
present genus the two pairs of outer and inner cones of the tetraconodont form are 
( 71 ) 
