162 FIELD COLUMBIAN MUSEUM ZOOLOGY, VOL. III. 



81; palatal length, 17; mastoid breadth, 14; width of brain case 

 above auditory meatus, 10.5; length of upper tooth row at 

 alveolar border, 8. 



This form of Microtus is allied to M. californicus, but is con- 

 siderably larger and usually has a reddish tinge to the pelage not 

 observable in the other, and is not so heavily lined with black. 

 Some specimens are quite reddish, being a dark tawny on all the 

 upper parts. 



It was not found on the coast north of San Quentin, and 

 ranges in the mountains east of that place to La Grulla and 

 Agua de las Fresas, about 8,000 feet elevation. North of these 

 places it was not seen. 



In the series of this form procured by Mr. Heller, slight 

 variations in color are observable among the examples, caused 

 probably by age, and as they were taken from July to September, 

 possibly also by the difference of season, although I should judge 

 that this was not a very potent factor, as some specimens taken 

 in July and September more nearly agree in color than some 

 procured during the interval. The tails are not all colored like 

 that of the type, some being dusky above and cream color 

 beneath, and some specimens are paler and less red than others, 

 and the form is not nearly so dark as M. californicus, of which it 

 is a subspecies. It is a large vole and belongs to the group 

 containing constrictus vallicola, scirpcnsis and the species men- 

 tioned above, and is even larger than M. vallicola, which up to 

 this time exceeded in size any of the known species. 



GENUS FIBER. 

 Fiber occipitalis. Sp. nov. 



Type locality. Florence, Oregon. 



Gen. char. Size largest of the genus. Occipital crest bowed 

 inward at interparietal, nearly forming a half circle; interorbital 

 constriction greatly pronounced; frontal crest marked; post- 

 orbital processes pointing downward, acute; brain case narrow 

 posteriorly; interparietal nearly as long as broad; parietals pointed 

 anteriorly, very narrow posteriorly; nasals broad anteriorly, 

 sharply contracting posteriorly; face of occipital broader in pro- 

 portion to its height than that of F. zibethicus; coronoid process 

 of mandible narrow, acute; condyle broad and heavy; molars 

 smaller than those of F. zibethicus; incisors short, heavy. 



Color. Upper parts reddish brown, lined with black hairs, 



