1 8 8 2 . ] Geology and Paleontology. 7 1 



GEOLOGY AND PALEONTOLOGY. 



The Oldest Artiodactvle. — Members of this order have 

 been found in the upper Eocene of N. America ( Acluenodon), 

 but none have been determined as yet from the American 

 Suessonian or lower Eocene. A species represented by teeth 

 from the Siderolitic beds of Switzerland has been referred to 

 Dichobune ( D. coinpichii Pict) ; but dental characters alone 

 are not sufficent to distinguish that genus from the Peris- 

 sodactyle Plienacodontida? 1 . Dr. Lemoine found astragali of a 

 small Artiodactyle in the Suessonian of Reims, which he has 

 recently ascribed to his Lophioclnvnts peroni, which he believes 

 {Proceedings French Assoc. Adv. Sci., Montpelier, 1880) to be a 

 suilline. 1 have reported an astragalus from the Wind river for- 

 mation of Wyoming Territory, which is almost exactly similar to 

 those found by Lemoine. A specimen of MiocLcuus braehystomns 

 Cope now to be described, enables me to characterize with some 

 degree of completeness this interesting form, which precedes in 

 time all the known American . Irtiodactyla. 



The characters of the tarsus are typically those of the Order 

 Artiodactyla. The astragalus exhibits a distal trochlea which is 

 continuous with the sustentacular facet, and which articulates 

 with both cuboid and navicular bones. 



The distal portion of the fibula is free from the tibia, and its shaft 

 becomes very slender, but it is possible that a more perfect speci- 

 men would display it as continuous. Its distal extremity articu- 

 lates with the ascending tuberositv of the calcaneum. The cuboid 

 facet of the latter is narrow. The cuboid and navicular are dis- 

 tinct from each other and the cuneiforms; the mesocuneiform is 

 shorter than the ectocuneiform, and is coossified ivith it. 



There are probably four metatarsals. The median pair are dis- 

 tinct, but appressed ; their section together, subcircular ; the lateral 

 metatarsals are slender, the external one is wanting, but its facet 

 on the cuboid is very small. 



These characters are in general similar to those of the genus 

 Dichobune, but Cuvier 2 does not state whether the cuneiforms are' 

 co6ssified in that genus or not. They are united in Anoplotherium. 



Miochenus differs from Diclwbune in the presence of but one 

 internal tubercle of the superior molars, and in the single external 

 tubercle of the superior premolars. Both genera are referable to 

 a family to be distinguished from the Anoplothetiida by the 

 presence of external digits. This has been alu.-a.ly named by Gill 

 the Dichobunidcz. The genus Lopkiochcerus is not yet fully char- 

 acterized, but its inferior true molars are very elongate and have 

 their cusps connected by oblique ridges.— if. D. Cope. 



