ae 
1883. | 309 (Cope. 
extent, as it has been protected by basaltic outflows or not. When s0 pro- 
tected, the river flows through comparatively narrow cafions. Where 
the outflow is wanting, the valley of the river is wider, and the Loup 
Fork formation remains as wide grassy mesas which extend to the feet of 
the mountain ranges, 
The age of these beds would have remained problematical but for the 
fortunate discovery by Mr. Robert Seip, of the skull of a species of Rhi- 
noceros of the typical Loup Fork genus, Aphelops. It is apparently the 
A. fossiger Cope, a species abundant in the Loup Fork beds of Kansas 
and Nebraska. It was found near the mouth of Dry creek in a conglom- 
erate bed of the formation. 
In the valley of the San Francisco the Loup Fork beds reach a thick- 
ness of 500 feet, and consist of sand, clayey sand, soft sandstone, and 
conglomerates of larger and smaller pebbles of eruptive material, having 
® near resemblance to those of the region of Santa Fé. 
Second Addition to the Knowledge of the Puerco Epoch. By EB. D. Cope.* 
(Read before the American Philosophical Society, December 7, 1883.) 
Recent collections from the formation above-named, include many finer 
specimens than have been previously obtained, Skulls of several species 
in calcareous concretions were received, so that their characters can be de- 
veloped more fully than heretofore. I mention especially Deltatherium 
Sundaninis ; Periptychus rhabdodon and P. coaretatus ; Haploconus linea- 
tus ; H. entoconus ; Anisonchus sectorius ; Protogonia plicifera ; Mioclanus 
turgidus, M. ferow, M. subtrigonus and M. cuspidatus, sp. nov. Some species 
hitherto rarely seen, prove to be abundant, as Hemithlaus kowalevskianus, 
Protogonia plicifera, Mioclanus minimus and M. subtrigonus. With the 
additional species now described, the number of Mammalia from the de- 
posit of the Puerco epoch amounts to seventy-four species. 
DIpYMioris PRIMUS, sp. nov. 
That the genus Didymictis existed during the Puerco epoch, has been 
already demonstrated by the discovery of the D. haydenianus Cope. This 
species is of aberrant form however, so that it remained to prove that the 
typical form had appeared so early in Tertiary time. This is now shown 
to have been the case by the discovery of the present animal, which is 
allied to the D. leptomylus of the Wind River and Wasatch epochs. 
The Didymietis primus is known from two maxillary bones with teeth, 
*The “ First Addition” appeared in the Proceedings of the American Philo- 
sophical Society for 1888, beginning at page 545. Since that date I have described 
in the Proceedings of the Philadelphia Academy, 1883, p. 168, the following spe- 
cies: Periptychus courctatus, Pantolambda cavin , Zelodon gracilis (g.n.) and 
Conoryctes ditrigonus. 
