20 AGRIOCIIOERUS. 



of the two sides; its median suture being about five lines above the alveoLar 

 margin. (Fig. G.) 



Inferior Maxilla. — The two fragments of lower jaw, preserved in connection 

 with the specimen just described, and comprising as much of the body of each side 

 as contains the hinder five molars, present pretty much the same form as the cor- 

 responding portion of the jaw of the Camel, but are relatively deeper and less 

 convex externally. (Fig. 5.) 



The alveoli have a remarkable degree of descent forward in relation to the base 

 of the jaw; the depth of the bone below the posterior lobe of the last molar being 

 twenty-one lines, whilst it is only eleven lines below the last premolar. 



Internally the lower jaw is much more convex than externally, especially in 

 advance of the first true molar, and also posteiior to this upon the alveolar portion 

 of the bone. 



Just above the thick, rounded base of the jaw internally, and below the position of 

 the first true molar, a concavity commences, which gradually expands and deepens 

 to a line with the posterior lobe of the last molar, when it abruptly increases and 

 then continues to the broken margin of the specimen, so that it is probable the 

 technical angle of the jaw within is deeply concave, as in the Tapir. 



A little more than half way below the position of the last premolar externally 

 is a small foramen directed backward, which is probably an offset from the inferior 

 dental canal. 



Dentition. — The molar teeth of Agriochoerus are certainly ruminant in their 

 type, and the true molars in both jaws are constructed upon the same pattern as 

 those of all recent ruminants, each being composed of two symmetrical pairs of 

 demiconoidal lobes, with an additional odd lobe to the last lower molar. In the 

 specimen above described, the posterior six molars are preserved in the upper jaw, 

 and the posterior five in the lower jaw. 



The molars in both jaws successively decrease in size from behind forward. 

 Those above, on the two sides, are nearly parallel internally, and from thirteen to 

 fourteen lines apart, but externally their line is convergent forward. 



Superior Molars. — (Figs. 5, G-10.) The upper true molars resemble very closely 

 the corresponding teeth of Hyopotamus deprived of their anterior median or ac- 

 cessory lobe. As in this genus, their transverse diameter is greater than that 

 antero-posteriorly ; the result apparently of the expansion of the teeth from the 

 condition in which they exist in the recent ruminants generally. The lobes are 

 low and spread wide apart, and the interlobular spaces are broad and shallow; 

 thus the perpendicular height of the outer lobes of the last molar is four lines, 

 and the distance between the summits of the anterior pair of lobes is three lines. 



The outer lobes conjoin externally to form a prominent median convexity, and 

 another, similar but not quite so large, is formed by the union of the anterior angle 

 of the antero-external lobe with the contiguous prolonged arm of the summit of the 

 antero-internal lobe. The surface of the outer lobes, between the external con- 

 vexities, is transversely concave with the feeblest degree of median elevation, and 

 inclines very much inward. Internally the outer lobes are convex and nearly 

 vertical. 



