616 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 5-j. 



C. leucurus. In C. ludovicianus the border is prolonged backward 

 as a distinct ridge as far as the second or third molar. In the fossil 

 it does not descend so close to the alveolar border as it does in both 

 of the existing species just named. The broad groove running 

 upward and forward in front of the anterior root of the zygomatic 

 arch is deeper and broader than in C. leucurus, especially anteriorly, 

 being more like that of C. ludovicianus. Along the middle of the 

 palate there is a sharp and prominent ridge, highest in front. This 

 is present in C. leucurus, sometimes becoming nearly as prominent 

 as in the fossil. 



Enough of the interorbital space is left to show that the width 

 was at least 11.5 mm. This width is very variable in C. leucurus. 



Cynomys niobrarius was probably larger than C. leucurus, since 

 the tooth row, measured on the alveolar border, is very close to 17 

 mm. long, and would certainly have exceeded this after the replace- 

 ment of the milk molars by the premolars. The three molars occupy 

 11.5 mm. of the alveolar border. No specimen of C. leucurus showed 

 quite so large a molar row. The species now occupying that region 

 is the typical C. ludovicianus. C. leucurus inhabits the mountainous 

 regions of Wyoming, Colorado, and New Mexico. ° 



CITELLUS TAYLORI, new species. 



Plate 120, fig. 7. 



Type specimen.— A left ramus of a lower jaw, with the premolar, the 

 molars, and a part of the incisor. Amer. Mus. Nat. Hist., New York. 



Type locality. — Probably somewhere in the vicinity of San Diego, 

 Texas. 



Type jormation. — Pleistocene. 



Diagnosis. — First and second molars wider than long. The anterior 

 transverse crest of moderate height. The premolar as long as wide; 

 the cusps of its anterior crest with a shallow notch between them. 



The type of this supposed species is a part of the Cope collection 

 in the American Museum of Natural History. It is labeled as having 

 been collected by W. Taylor, of San Diego, Texas, who was one of 

 Cope's collectors in that region. The jaw is further labeled as having 

 been found in the "elephant beds." The jaw and teeth seem to 

 resemble most those of Citellus townsendi — a species now living in 

 Oregon, Wyoming, and California. The molar teeth have the same 

 short, broad form, and the jaw itself is hardly different. The anterior 

 crest of each tooth is, however, not so high as in that species and not 

 so abruptly steep on its hinder face. The premolar of C. townsendi 

 and of various other species examined is shorter than wide; also in 



•Hollister, N. A. Fauna, No. 40, p. 24. 



