APPENDIX 



Aet. LYI. — A JVew Order of Extinct Eocene Mammals 

 (Mesodactyla) ; by O. (X Maesh. 



Dueing explorations in the lower Eocene deposits of New 

 Mexico, carried on by the writer in 1876-1880, some of the 

 first fossils discovered were remains of small mammals about 

 as large as a fox, and of much scientific interest. The teeth 

 are somewhat-similar to those of Ungulates, but the rest of the 

 skeleton, and especially the limbs and feet, are of a generalized 

 type quite distinct from any of hoofed animals known, recent 

 or extinct. Some parts of the structure seem to indicate an 

 affinity with Hyrax, but the limbs and feet show characters 

 resembling those of the Primates, especially the extinct forms, 

 and likewise seen in Insectivores, and even in some of the 

 Rodents. A large collection of these remains was secured, and 

 when examined was found to include several distinct forms, 

 all of small size, and forming together a natural group. 



One 'of these forms was described by Cope, under the name 

 Meniscotherium chamense, the type being a portion of an 

 upper jaw, with the molars in place.* This specimen was 

 subsequently described and figured by that author, who regarded 

 it as belonging to the Perissodactyles.f Later, he defined two 

 additional species, and proposed for the family the name 

 Meniscotkeriidai ; and more recently has described and figured 

 various parts of the skull and skeleton.;}; 



Several other authors since then have discussed the affinities 

 of this peculiar family, but mainly without presenting any 

 new facts bearing on the question, the general opinion being 

 that these animals are primitive forms of Perissodactyla, 

 more or less related to Chalicotherixim, Kaup, which genus 

 they resemble in dentition. A comparison of the feet would 

 have been more important, but those of Meniscotherium^ at 

 least, were unknown. 



*Eeport of Chief of Engineers for 1874, pt. ii, p. 596. 

 f Extinct Vertebrata, p. 251, pi. lxvi, 1871. 

 % Tertiary Vertebrata, 1 884. 



