416 PLAGIAULAX. 



and to the outer a single tubercle, which is situated more 

 anteriorly than in Plag. minor. The outer point is worn 

 down and indistinctly defined, the wear involving- what ap- 

 pears to have been the bevelled lunate rim at the posterior 

 end, as described in the other species. It is not determinable 

 whether it attained the magnitude of a separate tubercle. 

 The two inner points form obtusely conical tubercles, which 

 are in greater relief, and less affected by wear ; so that the 

 worn disc of the outer row looks like a step at their base. 

 Of these tubercles the anterior bears an accessory lobe which 

 is continued across in a front talon, giving a bilobed cha- 

 racter to the point, which is but slightly abraded at the apex : 

 while the posterior point shows a well-marked depressed disc, 

 which is continued some way down upon the inner side of 

 the enamel, as if caused by the grinding play of an over- 

 lapping cusp of an upper tooth in use against it. The lon- 

 gitudinal furrow between the two rows is distinctly visible. 

 There is a well defined basal cingulum to the last molar in 

 this species. The inside elevation of the last true molar 

 agrees very closely with a corresponding view of the larger 

 tooth of Microlestes antiguus, as represented in one of the 

 drawings belonging to Sir Charles Lyell (PI. XXXIV. fig. 8). 

 The second and last true molar presents a nearly square 

 crown with rounded angles. It is fully equal in size to the 

 penultimate, if not a little larger. The crown bears two 

 marginal edges, as in the other species, with a well-marked 

 depression between them. The inner edge is broken off and 

 seen embedded in the matrix of the opposite slab. The outer 

 edge is entire, but ground down by wear, so that it shows a 

 marginal band with no remains of crenation. The detrition 

 of the crown, as a whole, bears some resemblance to that 

 seen upon the last molar of an aged Bear ; the comparison, 

 be it understood, not being intended to imply the slightest 

 idea of affinity. The angle formed by the anticlinal planes 

 of the crowns of the true molars and premolars is more 

 acute in the jaw of Plag. Becklesii than in that of Plag. 

 minor. 



Character of the Power Jaws. — Although the teeth are seen 

 in greater perfection in the smaller species, the other cha- 

 racters of the jaw are best shown by the specimen of Plag. 

 Becklesii, PL XXXIII. figs. 1 and 4, a, b, and b, d. The jaw, 

 right ramus, is broken vertically through one of the sockets 

 of the first true molar; the anterior fragment (a, b) presents 

 the outer surface of all the teeth in front, from the last pre- 

 molar, while the posterior fragment {b, d) exhibits the inner 

 surface of all behind, on to the condyle. A very distinct im- 

 pression of the premolars attached to the anterior piece is left 



