5 70 Btdletin American Museum of Natural History. [Vol. XIX, 



Synopsis of Allied Genera. 



Mylodon} 

 Number of teeth in skull .... 5 



Number of teeth in lower jaw 4 



Character of last molar of 



lower jaw bilobed 



Character of first molar of 



lower jaw elliptical, 



opposes m- 



Character of muzzle slightly 



contracted, 

 ru8;ose. 



Generic Chronology. 



1840. Glossotherium Owen, Foss. Mam. Voy. Beagle, p. 57. No 

 species named. Type, the back of a skull from S. America. 



1840. Mylodon Owen, ibid., p. 86. Type, M. harlani, based on a 

 jaw found in Kentucky, which had been previously referred 

 by Harlan to his Megalonyx laqueaius. Referred species, M. 

 darwini, based on jaws, etc., from S. America. 



1842. Mylodon robustus Owen. Skull and skeleton. Glossotherium 

 here made a synonym of Mylodon. 



1855. Lestodon Gervais. Type, L. armatus, which {fide Lydekker) is 

 not generically distinct from Mylodon. 



1879. Grypotherium Reinhardt. Founded on skulls of JMylodon 

 darwini. 



1S80. Pseudolestodon Gervais and Ameghino. Type, Mylodon 

 gracilis = Lestodon my hides. 



1887. Lydekker, in his Catalogue of the Fossil Mammalia in the 

 British Museum, correctly states that M. harlani is the type 

 of the genus, and divides Mylodon into two groups: one 

 represented by M. darwini, the other including M. harlani, 

 along with M. robustus, M. littsomi, M. armatus, and M. 

 gracilis. In the first, "the first tooth in each jaw is ex- 

 tremely minute and wears horizontally." His reason for 

 placing M. harlani with the second group is, perhaps, that a 

 jaw shorter in front than the length of the dentitiop is indi- 

 cated in that species, as is the case in M. robustus, etc., while 

 in M. darivini the predentary portion of the jaw is much 

 elongated. 



1899. Neomylodon Ameghino. Type, N . listai. 



' M. robusHis. 



