184 



Annals of the Carnegie Museum. 



very heavy, and in the condylar process. The symphyseal suture is 

 large. The anterior part of the jaw is farther strengthened by a ridge 

 which passes from the upper part of the symphyseal suture obliquely 

 around the outside of the jaw backward and downward to the chin. 

 The anterior border of the coronoid process slopes upward and back- 

 ward uniformly, in a nearly straight line, to near the tip, where it is 

 broken off. The lower teeth are much smaller than those of Arcfomys. 

 The other parts of the skeleton so far as preserved are much like those 



of Arctomys. 



Measuremknts. 



Mm. 



Lengtli of skull loo 



Length from anterior of incisors to posterior of zygomatic arch 78 



Width of skull at post-orbital constriction 21 



Depth of snout just anterior to anterior root of zygomatic arches 27 



Depth just back of incisor 25 



Width just back of incisor 32 



Antero-posterior diameter of upper incisors 9 



Transverse diameter of upper incisors , 4.5 



Length of mandible including incisor 70 



Length of lower molar-premolar series 15. 5 



Depth of mandible of middle of symphysis I4.5 



Pal^arctomys macrorhinus sp. nov. 



No- 733- Figs. 24 and 25. 

 The type of this species is a skull, lacking the nasals and the pos- 

 terior portion of the cranium. The skull is very robust and about the 



Fig. 24. Pahnai-ctomys macro) hiniis {¥.0. Til). Lower Madison Valley. Skull 

 from right side. Natural size. 



size of that of Arctomys /iionax, but the region in front of the orbits is 

 very much deeper and wider. The incisors are also much larger. 



