February 19, 1869.] ^^ [Cope. 



PalEeozoic rocks of Indiana, Kentucky and Ohio, &c. By 

 Sidney S. hjon of Louisville, with 4 plates," wHch was re- . 

 ferred to a committee consisting of Mr. Lea, Mr. Cope and 

 Mr. Lesley. 



The Secretary, in the absence of Dr. Leidy, communicated 

 for publication a memoir " On the Geological Age and Equi- 

 valents of the Marshall Group. By Prof. A. Winchell." 

 Which was referred to a committee consisting of Mr. Lesley, 

 Dr. Le Conte and Dr. Leidy. 



A letter from Prof. F. Y. Hayden communicated "Notes 

 on the Geology of "Wyoming and Colorado Territories, No. 2, 

 with 6 wood cuts, already cut, and two ink sketches," which 

 was referred to the Secretaries with power to act. 



Prof. Cope exhibited and described a jaw of Mylodon an- 

 nectens from the post-tertiary rocks of South America. 



Prof. Cope exhibited the mandible of a gigantic sloth from the post-ter- 

 tiary of the Banda Oriental in South America. He stated that it belong- 

 ed to the genus Lestodon (Gervais) but approached in its characters the 

 jVIyodon of Owen. He pointed out the anterior canine teeth of Mega- 

 lonyx, the posterior canines of Lestodon, and the reduction of the same 

 in Mylodon to the character of small premolars, less than the molars. 

 In the species exhibited, the canine is removed to close proximity to the 

 molars, and was as large as the first, immediately following it. The species 

 differs not only in this respect, but in the form of this and other teeth 

 from the Mylodon robus£us (Owen) , to which it is nearly related. The 

 form of the symphysis is not very different, but is turned outwards at 

 the anterior angles and emarginate medially. The lateral margin con- 

 cave. The canine directed upwards, and more outwards than the mo- 

 lars. Its section presents longer straight inner and anterior sides, and a 

 short convex outer side, which is connected to the inner by an oblique, 

 slightly concave side. The second tooth or molar about the same size, 

 and of subtrifoliate section, the outer lobe more obtuse, and less strong- 

 ly separated by alveolar ridges than the two inner from each other. 

 Third molar quite- oblique, directed backward and inward, the section 

 composed of four arcs separated by alveolar ridges. Posterior part of 

 alveolus of last molar broken away, the anterior part narrower and more 

 oblique than any other tooth. 



Prof. Cope stated that the species seemed to be near the Lestodon 

 myloides of Gervais, which was however so briefly described as to be 

 scarcely recognizable. According to the characters of Lestodon, the 

 canine tooth appears to be at a greater distance from the molar than in 



