1886.] NATURAL SCIENCES OF PHILADELPHIA. 359 



OBSERVATIONS UPON THE UPPER TRIASSIC MAMMALS, DROMATHE- 



RIUM AND MICROCONODON. 



BY HENRY F. OSBORN, SC. D. 



In 1857 Prof. Emmons ^ described portions of three small mam- 

 malian jaws from the Upper Triassie (Chatham Coal Fields) of 

 North Carolina, which he assigned to the new genus Dromathe- 

 riuvi. The type-specimen is now in the Geological Museum of 

 Williams College. Another specimen is in the collection of the 

 Academy of Natural Sciences of Philadelphia. I cannot ascertain 

 the whereabouts of the third fragmentary specimen mentioned by 

 the author. I am indebted to Prof. Samuel F. Clarke, of Williams 

 College, for an opportunity of stud3dng the type specimen. 

 Although slightly injured in the original removal of the matrix, 

 this fossil is in beautiful preservation, and gives the complete 

 mandibular dentition, with the exception of two molar crowns. I 

 soon observed that my drawing, made under a camera, did not 



Microconodon and Dromatherium. Natural size. 



agree with that given by Emmons, in his American Geology, Part 

 YI, p. 94, which has since been copied by Owen, Dana and others. 

 This discrepancy was apparently explained later by a comparison 

 of the Williams College specimen with that in the Academy of 

 Natural Sciences of Philadelphia. In the latter, although the 

 mandible is nearly complete, two molars and two premolars only 

 are preserved, but these indicate a distinct genus. As Emmons 

 referred both jaws to the same genus, it is not unlikely that he 

 supplemented the rather obscure characters of the teeth in his 

 type-specimen with the very obvious tooth patterns of the less 

 perfect specimen. Thus, while the number of the molars in 

 Emmons' drawing follows the type-specimen, their form resem- 

 bles that observed in the Microconodon molars, which will pre- 

 sently be described. 



Those familiar with the works of Professors Owen and Marsh 

 upon the Mesozoic mammalia are aware that sharp distinctions 



1 American Geology, Part VI, pp. 93 and 94. 



