70 ANCHITIIERIUM. 



The surface, for attacliment of the external pterygoid muscle in advance inter- 

 nally of the glenoid articulation, is much less inclined than in the Horse; and at 

 the antero-ipternal part, as. in this, it presents a foramen conducting to the fora- 

 mina rotundum and spheno-orbitale. 



The latter, and the optic foramina, are of large size, and hold very nearly the 

 same relative position as in the Horse. 



The interpalatinc notch, as in the latter, expands as it approaches its bottom, 

 which is on a line with the interval of the fifth and sixth molar teeth. 



The hard palate is broken in the specimen, but it appears to have been about as 

 much arched as in the Horse, and the exit of the posterior palatine canals is just 

 in advance of the sides of the interpalatine notch. 



Liferior 3Iaxilla. — (PL X., Figs. 18, 19 ; XI. 5, 6.) As in the case of the alveoli of 

 upper jaw, corresponding with the shortness of the teeth relatively and compara- 

 tively with those of the Horse, the body of the lower jaw of Anchilherium is 

 proportionately less deep than in the latter. Its outer side is vertical and slightly 

 convex; its .base is thick and slightly convex forward; and its upper margin 

 rapidly ascends posteriorly, and curves in a sigmoid manner more backward to the 

 summit of the coronoid process than in the Horse. 



The coronoid process is curved like in ordinary ruminants, but* is relatively 

 shorter and broader. 



The condyle is very like that of the Horse, but the notch in advance of it is 

 relatively broader. 



The ramus, which in the Horse is very slightly depressed externally below the 

 position of the coronoid process, in the fossil is almost as much depressed as in the 

 Peccary. 



BentlUoii.— (PL X. 14-17, 21; XI. 1, 3-8.) Gervais^ states the formula of the 

 dentition of Ancldtlierium to be: — 



.33 11 .77 



111. can. r, mol. ~ — -. 



3 3 11 7 7 



It is extraordinary that Anchitlierium should be so much like Palaeothcrium in 

 the anatomical and ph3'siological construction of its teeth, and yet be so much like 

 the Horse in its skeleton. 



The crowns of the molar teeth of Ancldtherium are entirely devoid of cementum, 

 and in the adult are completely exserted. 



The specimens of Anchitherimn Bairdii, which we have an opportunity of 

 examining, contain in the upper and lower jaws all the molar teeth except the 

 first of the series. 



The posterior six upper molars (XI. 3, 4,) are nearly alike in form and size ; the 

 crowns, as in those of Palaeotherlum, consisting of two transverse pairs of lobes. 



The outer lobes, as in the genus just mentioned, are demiconoidal with triangular 

 summits, the basal angles of which are continuous with the extremities of inverted 

 U shaped ridges bounding the sides and bases of the external transversely concave 

 surfaces. 



The inner lobes are conoidal, and are prolonged outwardly to the antero-internal 



* Zoolog. et Palaont. Frang., p. Co. 



