149 
part 4 .] Lydeiker: Osteology of Merycopotamus dissitnilis. 
The lower molars are distinguished from those of Ruminants by tile transverse valley 
extending completely across the crown, instead of being confined to the outer side; whereas 
m Ruminants, the outer pair of cones are united nearly up to their summits, instead 
ol only at their bases, as in Mcrijoopotamus; further, the summits of the cones in Rumi¬ 
nants become wider, and the central infolds of enamel (the remnants of the primitive longi¬ 
tudinal valley) become deeper, and arc connected together only by a narrow neck, which soon 
becomes obliterated by wear, causing the enamel pits to become complete islands, which 
remain until the tooth is worn down nearly to its base; islands only appear for a very short 
period on the crowns of the teeth of Merycopotamus, owing to the shallowness of the 
enamel folds. In the molars of animals like the Giraffe and Rrcmatherium, where the 
enamel pits are connected together by a deep median fold, and consequently are a long period 
in becoming completely insulated, we have a remnant of a more generalized type of tooth, 
showing traces of the persistence of the primitive longitudinal valley of the Suine teeth. 
Measurements of skull. —The following measurements are taken from the cranium, 
figured in the “Fauna Antigua Sivalensis” (plate 67, fig. 1):— 
Length from occipital crest to superior angle of orbit 
Width at superior border of orbits 
Length of orbit ... 
Width across zygomatic arches 
Width at temporal fossa? 
Length from foramen magnum to free border of palatines ... 
Length from foramen magnum to last premolar ... 
Width of palate at second molar 
Length of three molars 
Length of last molar 
Width of ditto ... 
Length of second molar 
Interval between inferior border of foramen magnum and summit of occipital crest 
Width of widest part of supra-occipital 
Interval between external surfaces of occipital condyles 
Vertical diameter of foramen magnum... 
Transverse ditto ... ... 
Length of occipital condyle ... ... 
In. 
60 
4-0 
1*9 
7'4 
37 
4-4 
8*1 
1*9 
325 
1*24 
1*2 
10 
4*1 
27 
2*85 
1*05 
1*4 
1*3 
The dimensions of the skull of the adolescent animal from Burma (No. 212) mentioned 
above, as given by Dr. Falconer (“ Pal. Mem.” vol. 1 , p. 148), are as follows :— 
In. 
Width of nasals at base ... ... ... ... ... ... ... 1-9 
Extreme length of fragment ... ... ... ... ... ... 7 5 
Greatest contraction of muzzle ... ... ... ... ... ... 1*2 
Length of two (1 and 2) true molars ... ... ... ... ... ... 1-9 
Ditto of two last premolars ... ... ... ... ... about 1*3 
The dimensions of the lower jaw figured in “ Fauna Antiqua Sivalensis” (plate 67, 
fig. 4), are as follows :— 
Extreme length 
In. 
... 13*5 
Depth at middle of last molar 
2*45 
Ditto at second molar 
... 
2*9 
Depth of descending angle below last of molars ... 
... 
4*3 
Length from hinder extremity of last molar to canine 
... 
7*9 
Length of symphysis 
4*4 
Interval between canine and symphysis 
..c 
... 
It 
Thickness of inferior border below last premolar... 
... 
1-03 
Length of last molar 
... 
1*6 
Width of ditto ... ,,, ... ... 
in 
III 
... 0-9 
