90 CENOZOTC MAMMAL HORIZONS OF WESTERN NORTH AMERICA. 



LATE PHASE OF THE MID-PLEISTOCENE. 



The Conard fissure of Newton County, Ark.," contains a typical 

 forest fauna that lived in a region with open glades similar to the 

 present landscape. It is very rich in individual specimens. Of the 

 37 genera and 51 species of mammals represented, 4 genera and 24 

 species are now extinct. Twenty genera and 6 species which occur 

 in the Port Kennedy cave are also found here. Of the surviving 

 species many are now distinctly northern or boreal types, such as 

 Microsorex, Mustela americana, Erethizon dorsatus, Cervus canadensis. 

 There are also 7 species of amphibians and reptiles and 7 species of 

 birds. 



The Proboscidea, Edentata, Tapiridse, and Camelidae of the earlier 

 Pleistocene faunae have all disappeared or are not represented. 

 Only Equus and a machserodont (Smilodontopsis) survive. There is 

 no evidence of Homo. 



Among Carnivora, (1) Ursidse ( ZJrsus) are numerous; (2) among 

 Felidse-Felinae, Felis, subgenus Lynx; among Machaerodontinae, 

 Smilodontopsis (Brown), a surviving saber-tooth; (3) among Canidae, 

 Canis, Vulpes, and Urocyon; (4) among Mustelidae, Mephitis, Spilo- 

 gale, Brachyprotoma (an extinct skunk, also found in the Port Ken- 

 nedy cave fauna), Mustela, and Putorius; (5) among Procyonidae, 

 Procyon; among Insectivora, Blarina, Sorex, Microsorex, Scalops; 

 among Cheiroptera, Vespertilio and Myotis; among Rodentia, Lepus, 

 Microtus, Fiher, Neotoma, Reithrodontomys, Peromyscus, Castor, Geo- 

 mys, SpermopJiilus, Tamias, Sciurus, Arctomys, and the h^^stricomorph 

 Erethizon; among Artiodactyla-Dicotylidae, Mylohyus; among Cer- 

 vidae, Odocoileus; among Equidae, Equus (represented by a single 

 tooth) ; among Bovidae ?, the aberrant musk ox, Symbos. 



CONCLUSION. 



The conclusion is that North America promises to give us a nearly 

 complete and unbroken history of the Tertiary in certain ancient 

 regions, which are, after all, comparatively restricted. The middle 

 and upper Eocene is approaching solution, but the lower and basal 

 Eocene still require additional surveys. The chief remaining gap is 

 now in the Pliocene stratigraphy, which calls for very exact geologic 

 sectioning and most careful systematic or faunistic comparisons. 



Materials are at hand for an establishment of the Pleistocene 

 sequence, which will be of the greatest aid to geologists. Here espe- 

 cially the paleontologist must work with the greatest caution in the 

 identification and description of species. It would be easy by care- 

 less methods to separate two depositions which are actually closely 

 similar in age. 



a Discovered in 1903 by Mr. Waldo Conard. The fauna was explored in 1903-4 and described In- Bar- 

 num BrowTi in 1908: Mem. Am. Mus. Nat. Hist., vol. 9, 1908, pp. 157-208. 



