Cope. I 546 [Jan. 18, 



LKPTAUCHEWIA Leidy. 



Extinct Mammalia of Dakota and Nebraska, 1869, 122. Proceedings 

 Academy Pkilad'a, 1856, 88, (nomen nudum), loc. cit. 1656, 163 (nomen 

 nudum). 



As already remarked by Leidy, tbis genus is characterized by tbe pres- 

 ence of enormous vacuities of the superior surface of the muzzle. The 

 genus might be described as lacking the usual superior osseous wall of the 

 nasal cavities and maxillary sinuses. The generic diagnosis is as follows: 



Otic bullae inflated. Four premaxillary teeth. Nasal bones excessively 

 contracted, leaving a wide interspace between them and the maxillaries. 

 Symphysis mandibuli coossified. 



This genus has but a short range in time, not having been yet found out 

 of the Ticholeptus beds. It shows in its deficient ossification, and smaller 

 size, tbat this line of the family was approaching its extinction, its deca- 

 dence having already commenced in the genus Merychyus. The genera 

 which follow in systematic order, Cyclopidius and Pithecestes, exhibit the 

 last steps in the downward course. 



I. Infraorbital foramen above- P-m. iii. 

 " Three inferior incisors ; nasal sinuses to middle of orbit ; 



true molars .043 ; skull .135." (Leidy) L. major. 



"Nasal sinuses not extending so far posteriorly as in L. major ; 



true molars .032 ; skull, .101." (Leidy) L. decora. 



"Nasal sinuses reaching to front of orbit ; true molars .020 ; 



skull .085." (Leidy; L. nitida. 



Leptauchenia major Leidy. 



Proceedings Academy Philad'a, 1856, p. 163 ; 1857, 89. Extinct Mam- 

 malia, Dakota and Nebraska, 1869, p. 124, PI. XII, figs. 1-5. 

 Tributaries of White river, Nebraska. 



Leptaiichenia decora Leidy. 



Proceedings Academy Philadelphia, 1858, p. 88 ; 1857, p. 89. Extinct 

 Mammalia of Dakota and Nebraska, 1869, p. 127, PI. XII, figs. 6-20. 



Tributaries of White river, Nebraska. 



Leptauchenia nitida Leidy. 



Extinct Mammalia of Dakota and Nebraska, 1869, p. 129 ; PI. XII, figs. 

 21-22. 



White Earth creek, Dakota, tributary of the White river. 



CYCLOPIDIUS Cope. 



Proceedings American Philosophical Society, 1877, p. 221. Brachy- 

 meryx Cope, Ibidem, p. 220. 



Dental formula : I. -§- : C. { ; P-m. f ; M. f . Premaxillary bones much 

 reduced ; mandibular rami coossified. Otic bulla inflated. Prelachrymal 

 vacuities present, and confluent with enormous nasal vacuities, which are 

 due to the excessive reduction of the nasal bones. Orbit closed behind. 



