TITANOTHERIUM. (Mil 
(XVII. 2) presents a basal ridge, descending at its anterior and posterior margin to 
the masticating surface; but it does not possess a median salient ridge like that of 
Palacotheriwm, nor does it present the anterior characteristic fold of the Rhinoceros. 
The portion of this surface corresponding to the posterior lobe inclines inward, in 
its course downward, and the anterior portion of the same surface rises into a 
median longitudinal prominence, descending to the apex of the anterior lobe. 
The inner side (1) of the teeth is transversely convex, and forms a thick and 
deep cingulum, with a wide, obtusely rounded border, enveloping the bases of the 
inner lobes. . 
The latter, of which that anterior is very much the larger, are confluent their 
entire height, and are isolated from the outer lobes nearly to their base; thus de- 
stroying the principal transverse valley as it usually exists in the molars of [hi- 
noceros and Palaeotherium, and creating one antero-posteriorly (3, 4). 
The antero-posterior valley, at the position corresponding to the depressed in- 
terval of the outer lobes, communicates with a large and deep trilateral pit, homo- 
logous with the termination of the principal transverse valley in the molar teeth of 
Rhinoceros, and with a similar pit in the teeth of Paulaeotherium. Posteriorly this 
valley is connected with another, but smaller and shallower pit, which also finds 
its homologue in the Rhinoceros and Palaeothertum. In one of the specimens (4), 
probably the third premolar, the antero-internal lobe is more confluent with the 
corresponding outer lobe than in the other; and its internal cingulum is more 
irregular. 
In the trituration to which these teeth have been subjected, the enamel has been 
worn off from the masticating surface of the outer lobes, very nearly to the base 
of those within, leaving a broad tract of exposed dentine, which is bilobed inter- 
nally by the deep central enamel pit. In the supposed third premolar (4), this 
tract is continuous, anteriorly upon the summit of the antero-internal lobe, but in 
the fourth premolar, the summits of the inner lobes present a separate antero-pos- 
terior tract. 
The enamel of these teeth, except where worn, is slightly rugose, and, upon the 
outer lobes, externally exhibits numerous transverse undulating lines. It is thickest 
upon the inner lobes, where it is one line and a half; and upon the external part 
of the outer lobes it is about one line in thickness. 
The measurements of the two specimens, in their present condition, are as 
follows :— 
Inches. Lines. 
Antero-posterior diameter of third premolar : ; ; : : , 2 5 
Transverse diameter of third premolar : 5 : : : : ° 1 10 
Antero-posterior diameter of fourth premolar. . : : - : 2 il 
Transverse diameter of fourth premolar. 5 3 : : : : 1 9 
One of the fragments of the premolars above mentioned, exhibits the inner lobes 
entirely associated as one, and disconnected to their base from the outer lobes. This 
connate lobe has the form resulting from the confluence of an anterior larger cone, 
with another posterior and smaller (7). The sides of the connate lobe, where not 
affected by attrition, are rugose, and the summit presents a clavate tract of dentine 
with a border of enamel nearly one line and a half in thickness. 
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