INSTITUTE OF SCIENCE, PHILADELPHIA. 3/ 



of M. rolntstus. Its proportions indeed are so different, that it may be ques- 

 tioned whether it really belonged to the same animal as the preceding speci- 

 mens, and if so, in view also of the difference in the first lower molar tooth, 

 whether it does not indicate another genus. It resembles more nearly the 

 first molars of both jaws of Mcgalonyx in its proportions and form than it 

 does the corresponding teeth of Mylodon robustiis. In its proportions it is 

 like the last lower molar, but in form is more like the first one oi Mcgalonyx. 

 In transverse section it is elliptical, more convex internally, somewhat flat- 

 tened externally and indented slightly along the anterior third. The biting 



extremity descends in a point 

 at the anterior third, but to a 

 far less degree than in the lower 

 tooth. The point extends in a 

 transverse crest whence the 

 triturating surface slopes for- 

 ward in a short plane, and back- 

 ward in a longer sloping con- 

 cavity. An outline of the ex- 

 tremity of the tooth and of the 

 ^ - transverse section are repre- 



First upper molar tooth, Mylodon harlani. 1, outline of j • i i • • i 



lower extremity ; 2, transverse section. Sented m the subjoined WOOd- 



cut. The fore and aft diameter 

 of the tooth is 33 mm., the transverse diameter i8 mm. 



The remains of the Horse, of the Petite Anse collection, consist of half 

 a dozen broken vertebrae, portions of several limb bones, fragments of a 

 mandible and a number of teeth of several individuals which were about the 

 size of the largest variety of the Domestic Horse. Though they present 

 no anatomical characters distinguishing them from the corresponding parts 

 of the latter, from the circumstances under which they were found, in asso- 

 ciation with the remains of undoubted extinct animals, and at a considerable 

 depth, taken into consideration with similar evidence from other sources, it 

 is rendered probable that they belonged to an indigenous and extinct species 

 of Horse. 



Two specimens of the atlas show the following measurements : 



Breadth at the anterior or condylar articulation, . -91 mr"- 98 mm. 

 Fore and aft length of the vertebral arch, . . . 40 " 40 " 



The distal extremity of a humerus at the articulation is 84 mm. in 

 breadth. 



The distal extremity of a radius is 83 mm. in breadth, and at the carpal 

 articulation is 68 mm. wide. 



The distal extremity of a tibia has the greater breadth 95 mm. and fore 

 and aft 54 mm. 



