62 ARGHAEOTHERIUM. 



the lacbi'vnial bone, to about the middle of the position of tb# penultimate molar 

 tootb. 



Inferior Maxilla. — Of tbe lower jaw we bave tbe opportunity of examining only 

 several small fragments, but fortunately tbese are important ones, as from tbe form 

 of the superior molar teeth resembling very closely those of Choeropotamus, we 

 mio-bt expect to find a lower jaw constructed like that of this animal, which is far 

 from being tbe case. One of the fragments consists of tbe posterior extremity of 

 tbe right side, externally attached to a mass of matrix. (X. 7.) Tbe coronoid process 

 and condyle are broken, but they appear to bave preserved their relative proportion 

 and position to one another, which are as in modern suilline animals. The tech- 

 nical angle, which is preserved entire, is not prolonged into a hook as in Choeropo- 

 taiims, nor is it rounded as in tbe Hog and Peccary, but is almost rectangular, and 

 lengthened slightly backward and downward, as in tbe Deer; and it is thick and 

 convex at the apex. Tbe ascending ramus is broad, and, as in tbe Hog, is apparently 

 not depressed to any extent in advance of the position of the condyle. The pos- 

 terior border of the jaw is vertically concave; and, indeed, excepting the condyle 

 and coronoid process, the posterior part of the bone partakes of the form of that of 

 the Hog and Deer. 



The other fragments are portions of the lower jaw of both sides containing molar 

 teeth ; and are two inches in depth below tbe position of tbe first true molar. That 

 of the right side is an exceedingly interestiug and important piece (VIII. 2), for, as in 

 Anthracotherium, itjias a short obtuse process projecting from the base of the bone. 

 The direction of the process is outward and downward, and it is situated below the 

 pot<ition anteriorly of the last permanent premolar. From the outward curve of 

 tbe process the jaw above and on a line with it is concave. 



Dentition. — Of tbe permanent dentition of Archaeotherium Ave are acquainted 

 only with the posterior five upper molars, and tbe posterior four below. These are 

 constructed upon an undoubted suilline type, but approach none of the recent forms 

 so much as they do those of Hi/racofherium, or more those of Choeropotaynus, and 

 most, if they are not identical with, those of Enielodon. 



In tbe specimens, the molar teeth above mentioned form a close row in both 

 jaws, and their relation to one another is the same as in the Hog, Peccarj^, or 

 Hippopotam us. 



Superior Molars. — (VIII. 2; IX. 1, 3-5; X. 1.) The upper true molars are con- 

 structed after the same type as those of Choeropotamus and Hyracotheriwm, but differ 

 principally in tbe less extent of development of the basal ridge. 



Tbe crowns of the anterior pair of true molars are quadrate with convex sides, 

 .and internally as in Eutclodou magnum bave no basal ridge like that existing in tbe 

 other two genera mentioned. The grinding surface of these teeth presents two 

 transverse rows, 6acb of three conical lobes, of which those external and that 

 antero-internal are tbe larger, and are nearly equal in size; and the remainder are 

 subequal. 



Tbe enamelled sides of tbe loljes are corrugated and their apices ai'c excavated, 

 though feebly, compared with what they are in Hi/raeollierium and Choeropotamus. 



