190 FIELD COLUMBIAN MUSEUM ZOOLOGY, VOL. XI. 



Fiber spatulatus. 



Fiber spatulatus. Osgood, N. Am. Faun., No. 19, p. 36. Elliot, 

 Syn. N. Am. Mamm., 1901, p. 214. 



One specimen from Beaverton, Oregon. 



I place this example as F. spatulatus with a doubt. It differs 

 from F. occipitalis in being smaller in all its measurements, and of a 

 different color, not so rufous, and in having broader shorter nasals, 

 these measuring, in total length, 19.5; anterior breadth, n; posterior 

 breadth, 3; the type of F. occipitalis having the nasals 22, 10, 4, respect- 

 ively. Unfortunately the entire posterior half of the skull belonging 

 to the specimen is wanting, and so no comparison can be made to 

 ascertain if it possesses the peculiar arch in the occipital outline. 



FAM. GEOMYIDyE. 

 THOMOMYS. 



A. MEGASCAPHEUS. 

 Thomomys bulbivorus. 



Thomomys bulbivorus. (Richards), Faun. Bor. Amer. , 1829, i, 

 p. 206, pi. 18 B. Elliot, Syn. N. Am. Mamm., 1901, p. 222. 



Twelve specimens: 7, Beaverton; 5, McCoy, Oregon. 



The examples from Beaverton are darker generally than those 

 from McCoy, probably on account of age; the slaty plumbeous pre- 

 dominating. Mr. G. S. Miller has called attention, in his paper on 

 this species (Proc. Biol. Soc., Wash., 1893, p. 113), to the conspicuous 

 differences the T. bulbivorus exhibits in its skull from other species, 

 notably T. bottce with which he compared it. The central surface of 

 the exoccipital next the condyle is occupied by a deep groove running 

 obliquely to the axis of the skull, while in botta this is flat; the audital 

 bullae are flatter and less inflated. The pterygoids are very broad 

 laterally, strongly concave internally, with the hamuli converging at 

 the tips. The shape of the pterygoids with their converging hamuli 

 seems to be an important character, sufficiently so with the others 

 named and the great size of the species to separate it subgenerically 

 from all others of the genus THOMOMYS. Its great size alone would 

 serve to distinguish jt at any time. I would therefore propose for this 

 species *MEGASCAPHEUS as a subgeneric term, distinguished by the 

 characters already mentioned. 



Mr. Heller found this species fairly common in the vicinity of 

 Beaverton, but they dwelt, as he writes, in such a low, wet'country 



* pfyas, great, and ax.a<psi>s, a digger. 



