1883.] NATURAL SCIENCES OP PHILADELPHIA. 169 



of second true molar: anteroposterior, 'Oil; transverse, "OOO. 

 From the Lower Puerco beds. D. Baldwin. 



Pantolambda cavirictus sp. nov. Represented by a nearly 

 entire mandibular ramus with all the teeth represented excepting 

 the crowns of the incisors. The characters are seen, first in the 

 large size, the teeth having twice the linear dimensions of those 

 of the P. bathmodon ; and second, in the lateral prominence of 

 the inferior edge of the ramus, which produces a concavity of the 

 side of the jaw posterior to the canine teeth. It is the largest 

 mammal known from the Puerco formation. 



The inferior canines are strongly curved, so that the crown is 

 directed upwards and a little backwards. Both root and crown 

 have a round section, but the apex of the crown cannot be de- 

 scribed, as it is greatly worn by use in the specimen. The 

 incisive border is regularly convex, and the three incisors are not 

 of large size, the first being least, and the third largest. The pre- 

 molars and molars have the form of those of the P. bathmodon. The 

 latter present two Y's, the anterior narrower and more elevated. 

 In the former the posterior V is represented by a short crest. 

 The last molar is produced into a heel, which supports the pos- 

 terior branch of the posterior V, and no cusp. The first premolar 

 is one-rooted, and is separated from the second premolar by a 

 moderate diastema. The symphysis is not long, is regularly 

 curved upwards, and has a flat inferoanterior face. The canine 

 alveoli create a marked prominence on each side. 



Measurements. — Depth of ramus at diastema, m. "045 ; do. at 

 third premolar, '056 ; width of ramus below third premolar, '021 ; 

 length of bases of three incisors, •023 ; diameters of canine at 

 base: anteroposterior, '018; transverse, '018; diameters third 

 premolar: anteroposterior, '012 ; transverse, 'Oil ; diameters first 

 true molar: anteroposterior, -077; transverse, "014; diameiers 

 third true molar: anteroposterior, "022 ; transverse, '014. 



The jaw of this species is about the length of that of a large 

 tapir, but is deeper and more robust. The flare of the inferior 

 edge in front is suggestive of the structure seen in the Dinocerata, 

 and of the probabilit}^ that the Taligrada (to which Pantolambda 

 belongs) are the ancestors of that suborder as well as of the Pan- 

 todonta. The flare is related to the flange of Uintatherium^ 

 exactly as the similar ridge in Nimravus is to the flange in Ma- 

 chaerodus. 



Ztetodon gracilis, gen. et sp. nov. Char. Gen. — This genus 

 and species are founded on a broken lower jaw which contains the 

 second and part of the first true molars, and the fourth premolar. 

 The teeth are of very peculiar character. True molars consisting 

 of narrow crescents in two paii's, which ai'e both concave towards 

 each other, embracing a fossa. The posterior crescents soon 

 unite on attrition, closing the fossa, while the anterior are well sep- 

 arated, and only unite by their anterior apices. Each molar has a 



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