li^nO.] 93 



The anterior of the two teeth in the fragment appears to be the first premolar, 

 corresponding to that tooth in the Anoplotherium by its double fang. The body 

 of the tooth is not so broad as in the latter, and is more conical. It is convex 

 externally from side to side, and the base of the enamel is elevated, rounded, and 

 deeply emarginate at the position corresponding to the separation of the fangs, 

 but it projects at no place beyond the general surface of the crown except poste- 

 riorly where it forms a slight ledge or heel. Interiorly the general surface is 

 convex, but it rather forms a central rounded longitudinal prominence from which 

 the surface passes off slightly concave posteriorly and to an elevated line at the 

 antero-interior border of the tooth. The enamel has been worn off the end and 

 along its posterior border. The second premolar is implanted in the alveolus by 

 three fangs, two externally and the other internally. The body of the tooth is 

 cuboidal, but is greater in its transverse measurement than antero-posteriorly. 

 The external face is convex from side to side, and is not so long as that of the 

 first premolar. The enamel base is strongly emarginate between the fangs, is 

 prominent, rounded, and projects into a narrow edge anteriorly and posteriorly 

 about 2J lines below its edge. The anterior surface is directed obliquely inward 

 and forward. The crown has been worn down leaving exposed a large, trans- 

 versely oval islet of dentine, which is continuous with a similarly exposed sur- 

 face antero-externally. The posterior surface is nearly transverse, and is worn 

 into a concave depression from the pressure of the succeeding tooth in the row. 

 The fangs are large and strong ; the antero-external is implanted in the jaw 

 obliquely upward and forward, and the poslero-external vertically ; the interior 

 is larger than the other and is placed on a line posterior to the antero-external 

 fang. 



The interspace between the first and second premolars is triangular, and from 

 the attrition upon the posterior surface of the former and anterior of the latter, 

 has been occupied, in a state of rest, by the body of the first premolar of the 

 inferior maxilla. 



Posterior to the second premolar, the sockets alone for the three fangs of the 

 third premolar exist in the specimen. 



The surface of the superior maxillary bone is convex from above downwards. 

 The infra-orbitar foramen, from a smooth notch existing in the specimen, appears 

 to have been placed at_^the junction of the superior maxillary with the malar 

 bone. The palatine process is 3 lines in depth from the edge of the alveolus. 

 The ossa nasi are transversely convex. 



Measurements. The heigh th of the superior maxillary bone from the lateral 

 nasal suture to the edge of the alveolus on a line with the second premolar, is 3i 

 inches ; breadth of os nasi on same line f of an inch ; breadth of first premolar at 

 base externally \\ inches; transversely i an inch; second premolar antero-posteri- 

 orly ^ of an inch ; transversely f of an inch ; heighth of face from middle nasal 

 suture to the roof of the mouth on a line with the first premolar 2 J inches, on a 

 line with the third premolar 3 inches. 



The species of Archaeotherium I have named Mortoni in honor of my friend 

 Dr. Samuel George Morton, the excellent President of this Academy, 



