Vol. 6] 



Merriam: Virgin Valley and Thousand Creek. 



287 



low median ridge on the surface of the narrower posterior side 

 of the horn-core, this specimen approaches the modern Antilo- 

 capra a little more closely than does the type material. As nearly 

 as can he determined from the fragmentary specimen, the other 

 characters which separate the type of Sphenophalos from Antilo- 

 capra are as marked here as in the type specimen. 



Measurements op the Horn-Cores 

 Pronghorn 



No. 8298* No. 11887 No. 11888 No. I2S37 



Anteroposterior diameter at 

 narrowest point above the 



base 41.3 mm. 41.7 36.5 44.8 



Greatest anteroposterior diam- 

 eter 50. 51.5 43. 60. 



Transverse diameter measured 

 ured at the same point as 

 the least anteroposterior 



diameter 23.9 33. 28.4 27. 



* Calif. Mus. Vert. Zool. 



Dentition. — In the collections thus far obtained in the Thou- 

 sand Creek region there are quite a number of long-rooted molar- 

 teeth of antelope-like forms that show a considerable range in 

 size. Some of the specimens represent animals as large as the 

 existing Antilocapra, others come from much smaller forms. It 

 is probable that some of these teeth represent Sphenophalos 

 nevadanus. All of the cheek-teeth of antelopes from the Thou- 

 sand Creek region are closely similar in form and structure to 

 those of the Recent Antilocapra. Some of the larger teeth which 

 seem most appropriate in size to accompany the skull of Spheno- 

 phalos are noticeably similar in form to the corresponding teeth 

 of Antilocapra. 



The upper and lower molars are all lono-rooted, reachin»' 

 almost, if not quite, to the stage of development of the Recent 

 Antilocapra in this particular. 



Two upper molars from Thousand Creek resemble the cor- 

 responding teeth of the Recent Antilocapra, in form and size. 

 A third upper molar, no. 12610 (figs. 70a and 706), is similar to 

 M., of Antilocapra. It differs mainly in the shortness of the 

 wing or lobe developed on the posterior side of the tooth. A 

 hypsodont lower molar M 2 , no. 121504 (figs. 71a and 716), has 

 the same anteroposterior diameter as M, of Antilocapra, but is 



