part 4 -.] Lydekher : Osteology of Meryeopotamm dissimilis. 
147 
processes are in too damaged a condition in our specimens for comparison. The basi-occipi- 
tal is triangular in shape ; it is more rounded from side to side than iti Sus. but it lacks the 
median groove and the two tubercles which are found on the same bone in Hippopotamus. 
Bulla tympani. —There is a large somewhat ovate tympanic bulla, larger than that of 
Hippopotamus^ and more like that of Sus : the meatus auditorius externus is apparently 
tubular, and directed upwards, backwards, and outwards. 
Palate. —The palatines are produced backwards behind the last molar in the same 
manner as in 1Hippopotamus; their hamular processes have also the same shape and 
direction; the palato-unixilhivy suture, as far as I can make it out, seems to have extended 
as far as the line which divides the first and the second molars ; its upward hand is rounded, 
as in Sus .- in Hippopotamus it is elongated. The two lines of molar teeth are nearly parallel, 
as in Sus; they do not diverge anteriorly, as in Hippopotamus. 
Glenoid cavity. —The glenoid cavity of the squamosal is flat, and of largo size ; it has 
no process of the jugal bordering its outer side; in the latter respect it agrees with 
Hippopotamus and differs from Sus. 
Mandible. — The rami of the mandible are nearly straight: the distal extremity is 
rounded off : the symphysis is long, and slightly excavated ; it extends backwards as far as 
the first premolar; it, is somewhat expanded at the alveolus of the canine tooth; the condyle 
and ascending portion is not known ; the posterior extremity descends below the inferior 
border of the horizontal portion, as in Hippopotamus ; there is a deep notch in front of the 
descending plate. From the above characters it will be seen that the mandible is entirely 
Hippopotamiue in character, and broadly distinguished from those of both Sus and 
Ant/iracot/urium, in which the inferior border is nearly straight. 
Dentition. —The dental formula most probably was the same as in Sus and Hexaproto- 
don ; as much of the dentition as is known is given below, viz. :— 
?—? l—x 4—4(?) 3—3 
I C- P - H - 
3—3 1-1 4-4 3—3 
Incisors. —The incisors are at present unknown ; from the shape and direction of their 
alveoli they must have been of comparatively small and equal size ; they were in close opposi¬ 
tion and probably projected obliquely from the jaw, their cutting edges forming a segment 
of an ellipse. There is no sign of any abnormal development in any of them, and they 
must therefore have approximated much more closely to Sus than to Hippopotamus. 
Canines. —The canine is situated close behind and a little to the outer side of the third 
incisor ; its inner border is in a line with the molar series ; in both of the above respects it 
agrees witli the canine of Sus, and differs from that of Hippopotamus. The cross-section of 
the canine is trihedral; two angles are placed in the autero-posterior line of the jaw, and the 
third on the inner side; these teeth are somewhat curved, the upper one more than the 
lower; they .are not of larger size than the canines of the wild boar; the upper canine does 
not present the groove on its posterior surface which occurs in the corresponding tooth of 
Hippopotamus. 
Premolars. —There is a considerable diastema between the canine and the premolar 
series; there is no jaw known which contains the whole of the latter fepries in situ; the 
first premolar seems to have been implanted by a single fang, and was probably of very 
small size; the last three premolars were implanted by two fangs each. The hinder pre¬ 
molars are unsymmetrically conical teeth, of which the inner surface is flattened and nearly 
vertical; there are two grooves, and an intermediate ridge oil this surface; the outer surface 
is rounded: there are semi-trenchant edges at the junction of these two surfaces, looking 
fore-and-aft: there is an accessory column at the autero-internal angle; the enamel is marked 
