840 THE JOHN DAY FAUNA. 



Castok peninsulatus Cope. 



Bulletin U. S. Geol. Survey Terrs., 1881, VI, p. 370. American Naturalist, 1883, p. 53, figs. 9, 10. 

 Steneofiber f nebraacensis Cope, loc. cit., 1879, p. 55. 



Plate LXIII ; figs. 18-21. 



This species is about tlie size of a large prairie marmot — Cynomys ludovi- 

 ciamts. It was abundant in Oregon during the period of the John Day Mio- 

 cene. Leidy originally described the closely allied C. ?iebrascensis from tlie 

 WhiteRiver beds of Nebraska, but I have never obtained it from that for- 

 mation. Another and similar species, C. pansus Cope, is common in the 

 Loup Fork beds of Nebraska and New Mexico. 



Several well-preserved skulls from Oregon display characters not visi- 

 ble in specimens heretofore collected, and which enable me to make fuller 

 comparisons with the European C. viciacensis, so fully described by M. 

 Filhol.i 



The postorbital constriction is much greater in this species than in the 

 C. viciacensis, and greater than in the C. nebrascensis from the White River 

 beds. The straight anterior temporal ridges are in line with the superciliary 

 borders, and unite into a sagittal crest at the constriction. In the S. vicia- 

 censis they continue separate beyond this point one-fourth tlie distance to 

 the supraoccipital crest. The zygomata are wide, and the malar ridge is 

 very prominent anteriorly, overhanging the face, and curving rather abruptly 

 to the base of the muzzle. The latter is rather wide, with parallel sides, 

 and is flat above. The brain-case expands rather abruptly from the inter- 

 orbital constriction, and is rather flat above. The infraorbital foramen is a 

 narrow vertical oval and is situated low down in the vertical line Avith the 

 anterior extremity of the malar angular edge. It is a little nearer the line 

 of the first molar than the posterior border of the superior incisor. The 

 incisive foramina are relatively larger than in the beaver, and are chiefly in 

 ihe premaxillary bone. The palate between the anterior molars is as wide 

 iis the transverse diameter of the first molar. There is no distinct fossa of 

 the maxillary bone in front of the orbit as represented by Filhol in the C. 

 ■viciacensis. The pterygoid fossa is wide, with the inner process the longer, 



' £tude des Mammif ^res Fossiles de Saint-Grand-le-Puy AUier. Bibl. de l'£cole des Hautes £tudes, 

 XIX, Art. I, p. 44, 1879. 



