482 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 92 
owing to environmental or geographic factors, but probably in a 
greater measure to chance preservation and collecting procedure. 
The horses represented, and in particular Nannippus phlegon, appear 
to be the strongest clue to their relative positions. The stage may be 
considered as belonging in upper Pliocene time as represented in our 
North American continental sequence. It definitely falls in the 
interval which we now call Blancan. Among the other known faunas 
of Blancan age are those from near Hagerman,’ Idaho; Meade 
County,? Kans.; and several localities in California, including those 
currently recognized under the local faunal names Coso Mountains,* 
San Joaquin,* San Timoteo,® and Tehama.° 
The Curtis ranch horizon was immediately recognized by Gidley 
as being somewhat younger than the Benson level, but considered to be 
Pliocene also. The reasons given for regarding the Curtis ranch 
level as pre-Pleistocene were somewhat mingled with those intended 
for the Benson stage, but may be segregated for the later horizon as 
pertaining to the mastodont, glytodont, canid, “dA/erycodus,” and the 
rodents in general. Later work has shown, however, that Stegomasto- 
don is known elsewhere in Pleistocene deposits, and the Curtis ranch 
form appears intermediate between S. texanus of the Blanco and S. 
aftoniae. The latter is regarded as somewhat younger than true 
Aftonian. Glyptotherium arizonae is more advanced than the Blanco 
form, and glyptodonts in general are known from much later stages 
of the Pleistocene, as in Florida. The “canid” humerus (fig. 44), 
exhibiting an entepicondylar foramen, was found to belong beyond 
question to a cat, as were all other parts of the same skeleton found near 
the rather modern appearing canid skull and jaws. The “Merycodus” 
material (fig. 47) is recognized as being antilocaprid and probably 
belongs to the species that Frick has named Capromerya gidleyi. 
The rodents are all truly extinct species, but this does not preclude 
an early Pleistocene age. 
Gidley was inclined to disregard the presence of Z'guus in the fauna. 
The species represented is not determined, and although it appears to 
be true Hquus, it is not greatly removed from the Plesippus stage. 
This is shown in particular by a collection of upper teeth described in 
Gidley’s notes as coming from the same level and about a hundred 
yards from a quarry that produced one of the mastodonts, Canis 
edward, the small cat, and Gidley’s entire Curtis ranch rodent col- 
lection. Contributing to the evidence for a Pleistocene age assign- 
1C, L. Gazin, Proc. U. S. Nat. Mus., vol. 83, pp. 281-320, 1936. 
2C. W. Hibbard, Trans. Kansas Acad. Sci., vol. 40, pp. 239-265, 1937. 
§J. R. Schultz, Carnegie Inst. Washington Publ. 487, pp. 75-109, 1937. 
4J. C. Merriam, Trans, Amer. Philos. Soc., new ser., vol. 22, pt. 3, pp. 32-42, 1915. (As 
upper Etchegoin.) 
5 Childs Frick, Univ. California Publ. Bull. Dept. Geol., vol. 12, No. 5, pp. 314-334, 1921. 
®R. D. Russell and V. L. Vander Hoof, Univ. California Publ. Bull. Dept. Geol. Sci., vol. 
20, No. 2, pp. 11-21, 1931. 
