150—2 INDIAN TERTIAEY AND POST-TERTIARY VERTEBRATA. 
The crown carries three distinct ridges and a well-marked hind talon [ta). The 
ridges are divided by a median longitudinal cleft into an inner and outer moiety, 
which are not set in the same transverse line ; the valleys are completely blocked by 
outlying, or accessory, columns, and there are four distinct cusps on the hindmost 
ridge. The columns (fig. 2a) have a considerable forward inclination ; the enamel 
has deep vertical groovings ; and there is a considerable amount of cement in all the 
valleys ; while there is a distinct cingulum (<?) on the inner side. 
All the above characters are those of the molars of Mastodon pandionis, and if 
the figures of the present specimen be compared with the figure of the type upper 
molar given in plate V., fig. 5, of the present volume,' it will be seen that the two 
agree so closely with one another that they evidently belong to the same species. 
The type tooth is, however, less narrow anteriorly ; but a much-worn specimen 
figured in plate XXXII., fig. 4, of the first volume, under the name of M. falconeri, 
but referred to the present species on page 30 of the present volume, agrees more 
nearly in this respect with the specimen under consideration. The three teeth taken 
together afford a good example of the variation to which an homologous tooth of 
the same species is liable. The length of the present specimen is 3'7 ; its greatest 
width 2'4 ; its width at the first ridge 1‘7 : and the height of the inner column of 
the last ridge 2*0 inches. 
Last upper true molar. — The specimen represented in plate XVI., fig. 1, agrees so 
exactly with the last left upper true molar in the palate specimen of M. pandionis 
from the Punjab represented in plate XXX VA. of the first volume, that it may be 
certainly considered as the homologous tooth. The Perim specimen (of which the 
talon has been broken away) is important as exhibiting this tooth in a worn 
condition ; the Punjab specimen being almost unworn. The figure shows the 
characteristic corrugated enamel, which presents a crenulated aj)pearance in transverse 
section. The inner columns present irregularly shaped dentine islets, and not the 
distinct trefoils of Mastodon falconeri^ ; this being mainly due to the small development 
of the posterior accessory column {b). Cement is present in all the valleys. 
Mastodon perimensis. Falconer and Cautley. 
Second right upper true molar . — In plate XVI., fig. 2, there is represented the 
greater portion of a right upper true molar of a mastodon, collected by Mr. Fedden, 
which from reasons given below is considered to be the penultimate tooth of M. 
perimensis, which has lost the last ridge and talon : the three remaining ridges are in 
an unworn condition. The specimen agrees very closely with the much damaged 
homologous tooth figured in plate IX., figs. 5 and 6 of vol. I. of the “ Palaeontological 
Memoirs and also in general characters with the first and third upper true molars 
figured in plates XL. and XLII. of the first volume of the present work. All these 
four teeth agree in having tall columns, with deep and narrow transverse valleys, 
1 A side view on a small scale is given in Falconer’s “ Paleontological Memoirs,” vol. I., pi. XXXIV., fig. 7. 
2 Vol. I., pi. XXXII., fig. 1. 
