1857.] OWEN — PLIOLOPHUS VULPICEPS. 61 



The first molar, PI. III. fig. 2, m 1, shows, as usual, a greater 

 amount of attrition than the preceding premolar : its grinding sur- 

 face presents four low thick cones, two internal as well as two ex- 

 ternal : each external cone is connected with its opposite internal one 

 by a low ridge extending from the fore part of the external to the 

 middle of the internal one, and swelling into a tubercle, r and s, at 

 the middle of its oblique course. The cingulum, c c, seems to be 

 continued uninterruptedly round the crown of this tooth, thickest 

 at the fore and back part, and at the interspace of the inner lobes ; 

 and developing the small accessory antero-external tubercle, c'. The 

 outer lobes are connected together by a low plate, internal to the 

 cingulum. 



The degree of attrition to which this tooth has been subject has 

 exposed the dentine, which is surrounded by a belt of thick enamel 

 upon the summits of the four principal lobes and of the intervening 

 tubercles. This molar is implanted by two external roots and by a 

 broad internal one, longitudinally indented at the middle, and which 

 may divide where it lies deeper in the jaw. 



The second molar, m 2, is similar to, but rather larger than, the 

 first ; and the tubercle on the oblique ridge connecting the two hinder 

 lobes is less developed. The cingulum, c, is obliterated on the inner 

 side of the posterior lobe. The implantation of the tooth is like that 



Of Ml. 



The last molar is rather narrower behind than m 2 ; the tubercle, r, 

 on the anterior of the oblique connecting ridge is smaller : that on 

 the posterior ridge is almost obsolete. The hinder of the two inner 

 cones is relatively less and lower than in m 1 and m 2, and is 

 scarcely defined from the oblique ridge s ; the cingulum is inter- 

 rupted at its inner base : the talon, t, formed by the back part of 

 the cingulum is better marked than in the other molars. In all these 

 teeth the enamel is wrinkled by longitudinal wavy impressions. 



Of the mandibular teeth, PL IV. figs. 4, 5 & 6, only the molar 

 series remain to be described. 



The first premolar, PI. II. figs. 3 & 4, p 1, is small, simple, sub- 

 compressed, conical, like the one above ; but it stands apart, an in- 

 terval of about half its breadth dividing it from the second premolar. 



This tooth, ib. pi 9 of rather larger size, has a similar form, but 

 with a better-marked hinder talon. 



In the third premolar, PL III. fig. 6,^)3, the talon, c, is developed 

 into a second lobe, which is lower than the first. The first or front 

 cone, a, shows a small anterior or antero-internal talon, and the apex 

 of the cone is cleft ; a ridge from the inner division, b, being con- 

 tinued obliquely down to the inner angle of the base of the low hinder 

 cone, c. 



In the fourth premolar, fig. 6, p 4, the division and development 

 of the anterior lobe has proceeded to establish a pair of cones, one 

 external, a, the other internal, b, connected anteriorly by a basal 

 ridge, in front of which is the fore part of the cingulum. The low 

 posterior lobe, c, shows the rudiment of a second internal cone, d. 

 The cingulum is developed at the fore part, and feebly between the 



