No. 2391. DESCRIPTIONS OF PLEISTOCENE VERTEBRATA—HA V. 615 



the fossil, 8 mm. The interorbital space of the former is transversely 

 concave; in the latter it is flat. The nasals of the fossil were con- 

 siderably wider than those of T. bottae leucodon. 



The lower jaw has the same length as that of the specimen of 

 T. b. leucodon, No. 4783, mentioned above. In the latter the incisors 

 project beyond the extreme end of the jaw 10 mm.; in the fossil they 

 project only 7.4 mm. 



The fossil skull appears to resemble still more closely that of 

 T. bottae nigricans, a form inhabiting the region about San Diego, 

 California. In this again the incisors project beyond the bone more 

 than in the fossil, and they appear to be somewhat more strongly 

 curved downward. The interorbital space is 7 mm. wide and trans- 

 versely concave. The ridges form the same lyriform figure as in the 

 fossil. The nasals overlap the frontals more than they did in the 

 fossil. 



The species here described is named in honor of Mr. N. P. Scudder, 

 librarian at the United States National Museum, to whom the writer 

 has been greatly and for a long time indebted for assembling the 

 literature that he has required in his studies. 



CYNOMYS NIOBRARIUS, new species. 



Plate 122, fig. 7. 



Type specimen. — A part of the skull which presents the palate and 

 its teeth; part of the interorbital space; and the bases of the zygo- 

 matic arches (No. 2715, American Museum of Natural History, New 

 York). 



Type locality. — Niobrara River, near Grayson, Nebraska. 



Type formation. — Sheridan beds of the Pleistocene. 



Diagnosis. — Allied to G. leucurus, but appears to have differed in 

 being larger and in having a broader and deeper groove for the 

 anterior branch of the masseter muscle. 



The label on this specimen states that it was collected by the 

 American Museum expedition in 1897. It is a thoroughly mineralized 

 fossil and was evidently buried in sand. The third milk molar is 

 present on the left side. On the right side it is missing, but deep in 

 the socket is seen the uncut third premolar. The next tooth behind 

 on each side is probably the fourth milk molar. All three molars 

 on each side are present. 



The bases of the zygomatic arches are somewhat injured, but they 

 show that the anterior border of the upper root approached the 

 premaxilla as it does in G. leucurus, and not nearly at a right angle, 

 as it does in G ludovicianus. The lower border of the anterior root 

 of the zygomatic arch ends abruptly opposite the first molar, as in 



