MURINE— ARVICOLINyE— FIBER. 253 



The stout zygomata do not dip down nearly to the palatal plane; the 

 maxillary plate supporting them in front is large; behind, they curve up to 

 the squamosals with moderate angularity. The arch is expanded in the 

 middle, much as in the Lemmings and the stouter Arvicolas, chiefly by the 

 laminar character of the jugal at this point; but the jugal is a mere splint, 

 not forming by itself any part of the continuity of the arch, for the squamosal 

 and maxillary spurs are absolutely in contact. This is a strong point of Fiber, 

 for in other Arvicolines these spurs, however closely approximated, do not 

 suturally unite. The parietals and interparietal are at a minimum size, coin- 

 cident with the encroachment of the highly developed squamosals; behind, 

 the squamosal vacuities are large; in front, this bone protrudes as an angular 

 process into the orbital space, but this is merely an exaggeration of the 

 smaller protuberance of other Arvicolince. The constriction of the frontal in 

 the interorbital region is at a maximum, the skull being here obviously nar- 

 rower than the rostrum. The nasals and intermaxillaries are of about equal 

 lengths; neither extend beyond the anterior root of the zygoma. In the 

 adult, the occipital bone shows no trace of its elements ; the paroccipital 

 processes are lengthened spurs ; the upper border of the bone forms, with 

 the continuous squamosal border, a strong sinuate crest, separating the 

 parietal from the occipital plane. The foramen magnum is usually emarginate 

 superiorly. The auditory bullae are not peculiar. The palate ends behind 

 opposite the middle of the last molar as a doubly emarginate shelf, showing 

 a median azygos protuberance with a fossa on either side ; it shows likewise 

 other lateral fossse or canals along its surface. The incisive foramina are 

 relatively short and constricted ; they rarely, if ever, reach to opposite the 

 molars behind, nor more than two-thirds the distance thence to the incisors 

 in front. The rostrum is tumid and obtuse, the nasals falling far short of a 

 perpendicular tangent to the incisors. In all this, it will be observed, Fiber 

 shows slight specialization of ordinary arvicoline characters. 



Externally, however, the modifications are stronger, in face of special 

 habitus. The under fur is even more woolly than in the Lemmings, and the 

 pelage is further conspicuous for the many stiff and glistening hairs with 

 which it is beset ; besides these, the antibrachium has a peculiar fringe of still 

 stiffer bristles. The sides of the hands and feet are likewise fringed with 

 hairs, but the soles and palms are perfectly naked ; above, these members are 

 closely pilous with very short adpressed hairs. The palms have five tuber- 



