1SSC] ^57 [Cope. 



on the other hand, does its principal wearing on down grades, and espe- 

 cially in cataracts, or, where falling over precipices or obstructions, it can 

 dash the stones, or other grinding material with which it may be charged 

 against the rocky bed below. In such places the erosion caused by ice 

 would be very insignificant or nil. Every one is acquainted with the fan- 

 tastic forms and miniature pot-holes made in the rocky bed of a stream 

 where it pitches down a cataract. Such cases are common in the carbo- 

 niferous shales along White Oak run and Laurel run near Archbald, and 

 in the Chemung and Portage rocks of Central New York. In addition to 

 these more specific differences, there is an indefinable one in the softer 

 outlines and appearances of a water-worn surface which generally aids the 

 experienced eye. 



Immediately to the north of the lower pot-hole a ledge, that is now 

 breaking up, has this water- worn appearance. Some of the best evidences 

 of the action of water may be seen about 500' N. 40° W. from the mouth 

 of this hole, and at the foot of the little hill that rises to its north. Here 

 the evidences of wearing by a large stream are unquestionable, although 

 there is now no considerable stream nearer than the Lackawanna at 

 Jermyn, more than a mile and a half away, and 210' below this level. 



On Two Neio Speaics of Ihree-toed Horses from the Upper Miocene, with 

 Notes on the Fauna of the Ticholeptus Beds. By E. D. Cope. 

 i 

 {Read before the American Philosophical Society, February 19, 1886.') 



Anchitherium ultimuji, sp. nov. 



Unusual interest attaches to this horse since it is the latest representa- 

 tive in time of the genus to which it belongs. It is from a horizon above 

 the John Day Miocene, which contains several Loup Fork genera and 

 species, as Protolabis, Hippotherium and Dicotyles. As, however, the 

 Blastomeryx borealis Cope occurs at the same locality and horizon, the bed 

 is probably to be referred to the Ticholeptus epoch, which I have shown 

 to be between the John Day and Loup Fork epochs in age, with greater 

 affinities to the latter.* The principal locality is the valley of the Deep 

 river, Montana, but the present species is derived, with those above men- 

 tioned, from Cottonwood creek, Oregon. 



The Anchitherium ultimum is represented in my collection by a nearly 

 complete superior dentition, with palate and sides of skull to the middle 

 of the orbits, and top of skull to above the infraorbital foramen. The size 

 is less than that of the A. praistans Cope and A. equiceps Cope (? A. 

 anceps Marsh) of the John Day bed, and the dental series has the same' 

 length as that of the A. longicriste Cope, also of the John Day. The animal 

 is adult, and anterior teeth are considerably worn. The posterior molars 

 * See American Naturalist for April, 1886. 



