298 



University of California Publications. 



[Geology 



A broken vertebra from the posterior cervical region (5th?) 

 seems to have larger zygapophyses than in the corresponding 

 vertebra of Antilocapra. In a middle dorsal vertebra the zyga- 

 pophysial faces are also relatively large, and the centrum is 

 relatively low. Several lumbar vertebrae present in the collec- 

 tions have longer and lower centra than in Antilocapra. In one 

 of these the spinal nerve passed through a foramen situated sev- 

 eral millimeters in advance of the posterior margin of the neural 

 arch. 



ILINGOCEROS or SPHENOPHALOS 



Several fragmentary specimens representing the dentition of 

 antelope-like forms from Thousand Creek resemble those referred 

 to Sphenophalos in most respects, but are smaller and may belong 

 with some of the forms referred to Ilingoccros. 



A portion of the upper jaw, no. 12613 (figs. 68a and 686), 

 with P 3 to M 1 represents an animal somewhat smaller than Antil- 

 ocapra or than the teeth tentatively referred to Sphenophalos 

 nevadanus. The teeth are apparently hypsodont, though con- 

 siderably reduced by wear. M 1 is slightly narrower than in 

 Antilocapra and the median rib on the outer side of the para- 

 cone is more prominent than in that form. P 4 is considerably 

 narrower and apparently a little less advanced in the develop- 

 ment of the crescents. The form represented by this jaw evi- 

 dently belongs to a species distinct from that in which the larger 

 teeth referred to Sphenophalos nevadanus are included. It may 

 correspond to a smaller species of Sphenophalos, or may repre- 

 sent one of the species in the group of twisted-horned forms 

 included in the genus Ilingoccros. 



A smaller upper molar, no. 12605 (figs. 69a and 696), and 

 a lower molar, no. 12612. may be referred tentatively to the 

 same group as the upper jaw fragment, no. 12613. They are 

 both hypsodont, and resemble Antilocapra in most respects. The 

 upper molar, no. 12605, is smaller anteroposteriorly and trans- 

 versely than in Antilocapra, and possesses a minute style between 

 the protocone and hypocone pillars. The lower molar, no. 12612, 

 is shorter anteroposteriorly and considerably narrower than in 

 Antilocapra. Both of these specimens evidently belong to a 



