Cope.] _ ^ [May 16, 



GLYPTODON Owen. 



Glyptodon, sp. indet. 



A nearly complete carapace of this remarkable animal is mounted in the 

 Museum Nacional, and a second, nearly as well preserved, is in the Mu- 

 seum of the School of Mines. Jaws and teeth occur in the latter museum. 

 The discovery of this genus at this extreme northern locality is due to 

 Dr. Antonio Castillo. It was first announced by Dr. Mariano Barcena in 

 the Revista Cientifica of Mexico, 1882, I, p. 3. The extension of this far 

 southern genus to the latitude of Mexico during the Pliocene (Pampean) 

 epoch, is entirely consistent with the further distribution of the great 

 sloths and llamas to the United States at the same time. 



DIBELODON Cope. 



Mastodon pars, auctorum. 



Various attempts have been made to define as genera groups of species 

 which are included within the limits of the genus Mastodon of avxthors. 

 The first new name, Tetracaulodon, was introduced by Dr. Godman, who 

 saw in the mandibular tusks of some individuals of the Mastodon ameri- 

 canus Cuv., ground of its separation from the genus Mastodon, in which 

 he believed those teeth to be wanting. This division was adopted by Dr. 

 Grant and others, but has not been generally allowed. The next division 

 was that proposed by Dr. Falconer, who, however, did not employ the 

 names proposed by him in more than a subgeneric sense. He distinguished 

 two series in the genus Mastodon. In one of these, the P-m. 3, and the 

 Ms. 1 and 2 present three transverse crests, while in the other division 

 these teeth present four such crests. To these divisions he gave the names 

 of Trilophodon and Tetralophodon respectively. The third attempt at 

 division is that of Herr Vacek, who gives names to the two divisions of 

 the genus in which the cross-crests are composed of tubercles or continu- 

 ous ridges. These divisions he calls Bunolophodon and Zj^golophodon 

 respectively.* 



I will refer to these divisions in reversed order. Those proposed by 

 Vacek cannot be regarded as genera, and their author did not use them as 

 such. The tubercular crest passes into the straight crest by insensible 

 stages. The divisions proposed by Falconer are more distinct, but not 

 sufficiently so to represent genera. This may be understood by reference 

 to the second lower molar of the Mastodon augustidem, which is, in some 

 individuals, three crested, and in others four crested. Some other species 

 present the same difficulty. On this point I quote the remarks of Dr. 

 Lydekker :f "The foregoing survey of such a large series of Mastodon 

 molars has led to the conclusion that the very regular ridge formula given 

 by Falconer will not always hold good in regard to the true molars, 



* Vacek, Ueber Oesterreichische Mastodonten. Abh. der K. K. Geolog. Reich- 

 anstalt, vii, Heft iv, Wien, 1877. p. ii. 

 t Geological Survey of India, Series x, Vol. i, pt. v, 1880, p. 256. 



