THE FOSSILS OF THE GRAVEL SERIES: BISON LATIFRONS. 247 
parts of North America. They have been referred to several extinct species, 
but the materials have been too incomplete to determine the question with 
any degree of satisfaction whether they pertain to more than one. The 
fossils indicate individuals very greatly differing in size, but the difference is 
perhaps sexual rather than specific.” 
The finest specimen ever discovered in California was found in Pilarcitos 
Valley, a few miles south of San Francisco, imbedded in blue clay, twenty- 
one feet beneath the surface. It has been figured and described by Leidy, 
under the head of B. datifrons.* It consisted of the cranial portion of a skull, 
with both horn-cores. Two fragments of the lower jaw of B. latifrons were 
obtained in connection with remains of elephant and mastodon, near Miller- 
ton, Fresno County.t Of these specimens Dr. Leidy’s notes give the follow- 
ing description : “ One of the fragments is a portion of the left ramus of the 
lower jaw containing part of the second and the last true molars. The teeth 
have advanced to that position that the crowns have wholly protruded. They 
agree in their proportions with those represented of B. datifrons, which proba- 
bly is the male of the same species [B. antiquus]. The other fragment is a 
portion of the right ramus, and contains parts of the hinder pair of premolars 
and the succeeding pair of true molars. Measurements derived from the 
specimens are as follows : — 
Length of the true molar series i : : : . 56 lines. 
Fore and aft diameter of last true molar : . - 24 
Depth of jaw below middle of last true molar . : z coor, 
Depth of jaw below middle of first true molar. : 2 5 
Another specimen, which came from Kincaid Flat, near Sonora, consisted 
of two inferior molars, with the dentine decomposed and in a fragmentary 
condition, and was considered by Leidy as belonging to B. latifrons. It was 
stated to have been found at a depth of eighteen feet in the auriferous detri- 
tus of that locality, which has already been noticed. 
Still another specimen, referred to the same species, consisted of a lower 
molar, in a similar condition to the last. It was obtained at Saw-mill Flat, 
not far from the last-named locality ; and was stated to have been found at 
twenty feet indepth beneath the surface. Other specimens representing the 
same animal have been obtained at various points in the Coast Ranges. 
An interesting group of fossils was discovered by Mr. C. D. Voy, when ex- 
* Contributions, &., p. 253, and Plate XXVIII. 
t The locality will be more exactly designated under the head of the Elephant. 
