20 FOSSIL MAMMALIA OF THE 



Li the hindmost tooth (fig. 27, c) the two outer cones are broken off, showing that their 

 common base is divided from the two middle cones by a deeper groove than that which sepa- 

 rated the two outer cones from each other. 



Thus, the crown of these molars might be described as supporting three parallel 

 antero-posterior ridges ; the outer (fig. 29, o, o) and the inner (fig. 28) ridges being 

 each divided by an oblique cleft converging forward towards the middle of the tooth ; 

 whilst the middle ridge is divided by a curved cleft having its concavity turned forward 

 (fig. 30). 



The more mutilated state of the front tooth (fig. 27, a), of which only the base of the 

 middle ridge of the crown remains, throws no additional light on the modifications of the 

 very remarkable type of the grinding surface of the mandibular molars of Stereognathus. 



This type of tooth differs from that of all other known recent or extinct Mammals. 

 The nearest approach to it is made by the true molars of some of the latter from the 

 most ancient of the Tertiary strata, as, e.g. Pliolophiis, from a septarian nodule of the 

 London Clay^ (PI. I, fig. 31, lower molar), and Hgracotherium} 



The proportional size and regularity of form of the cones of the grinding teeth of the 

 Stereognathus give a different character of the crown from that of the multicuspid molars 

 of the Insedivora, and cause it to resemble more the pentecuspid or sexcuspid molars of 

 the extinct hoofed genera above cited. No Mesozoic Mammal save Stereognathus ooliticus 

 shows better grounds for being regarded as a diminutive form of the Ungulate order of 

 Mammalia; but, assuming its position in that order, it is probable that its food, if we 

 may judge from the existing Hogs and Peccaries, was of a mixed nature. There is cer- 

 tainly no other known Mesozoic Mammal which has so good a claim to be considered in 

 any degree herbivorous. 



Dr. Emmons has described and figured the mandibular ramus, 9-lOths of an inch in 

 length, of a Mammal (fig. 3) from the ' Chatham Coal-field' in North Carolina. It contains 

 three incisors, one canine and ten molars ; of the latter series, the first three have simple 



subcompressed conical crowns, the next four are multi- 

 cuspid, and the last three are tricuspid (according to the 



figure) ; the incisors are separated by intervals, as in 

 Myrmecohius and Phascolotherium. 



I opine that Dromatherinm was Marsupial. The extinct 

 species indicated by this mandible Emmons calls ' Broma- 



Dromatherium sylvedre. ii • 7,jrrM ^ • ^ • n • i 



Mno^n9,K„v, ii,n T? \ therium sylvestre. The carbonized remams of ancient 



Magn. Z uuim. (After iiinmons.) </ 



vegetation in which the foregoing, with two other similar 

 mandibular fossils, have been found, is probably, like the coal of Brora, Sutherlandshire, 



1 <■ 



Quart. Journ. Geol. Soc.,' vol. xiv, p. 54, pis. ii — iv. - ' Geol. Trans.,' 2nd ser., vol. vi, p. 203, pi. 24. 



