PLIOLOPHUS. 363 



size to the penultimate molar in the upper, and to the last 

 molar, m 3, in the lower jaw, which tooth has a third lobe. 



In the last premolar upper jaw (fig. 123,^? 4) the two outer 

 cones resemble those of the true- molars ; but there is only 

 one inner cone, and the crown is triangular. A ridge is con- 

 tinued from the interspace between the anterior talon (c), and 

 the outer anterior lobe obliquely inward and backward to the 

 inner lobe, swelling into a small tubercle at the middle of its 

 course. 



The first molar (m 1) presents four low thick cones, two 

 internal and two external : each external cone is connected 

 with its opposite internal one by a low ridge, swelling into a 

 tubercle at the middle of its oblique course. The second 

 molar (m ^) is similar to, but rather larger than, the first ; 

 the tubercle on the oblique ridge connecting the two front 

 lobes is less developed. The cingulum is obliterated on the 

 inner side of the posterior lobe. The last molar is rather 

 narrower behind than m 2 ; the tubercle on the anterior of the 

 oblique connecting ridges is smaller : that on the posterior 

 ridge is almost obsolete. 



In the last lower premolar (fig. 124t,p 4) the division and 

 development of the anterior lobe give rise to a pair of cones, 

 one external (a), the other internal (6), connected anteriorly 

 by a basal ridge, in front of which is the fore part of the 

 cingulum. The low posterior lobe (c) shews the rudiment of 

 a second internal cone (d). 



The first lower molar (fig. 124, m 1) has a pair of front 

 lobes and a pair of hind lobes, with an oblique ridge con- 

 tinued from the postero-internal lobe to the interspace between 

 the front pair. 



The second molar (m 2) shews an increase of size; but 

 its chief and most interesting modification is the development 

 of a tubercle (e) between the two anterior lobes, making 

 three cones on the same transverse line, and thus repeating the 



