Article XIX. DESCRIPTION OF A NEW MOUSE FROM 

 LAKE COUNTY, CALIFORNIA. 



By J. A. ALLEN. 

 Sitomys robustus, sp. nov. 



Similar in proportions and coloration to Sitomys americanus gambelii, but 

 nearly twice the bulk of that form ; hence about equaling S. gilberti in. size, 

 but differing from the latter in much smaller ears and much shorter tail, and 

 also in coloration. 



Above uniform dull yellowish brown, much varied with blackish, the pelage 

 being plumbeous at base, subterminally broadly ringed with fulvous and tipped 

 with blackish ; middle of back darkest, gradually becoming more fulvous on the 

 sides, without, however, forming a distinct fulvous lateral line nor a distinct 

 dorsal band of dusky ; beneath white, as also the upper surface of both fore and 

 hind feet. Ears moderate, in size, form, color and hairiness about as in S. a. 

 gambelii. Feet large ; soles sparsely haired posterior to the last tubercle. Tail 

 a little shorter than head and body, sharply bicolor, dusky brown above and 

 white below, fairly well clothed with short hairs and non-penicillate about as 

 in S. americanus. 



Measurements. Two specimens, both males, and measured in the flesh by 

 the collector, give the following dimensions : Total length, 174-175 mm.; head 

 and body, 94-102 ; tail, 1 73-80 ; hind foot, 21-22 ; ear, 19-21. 



Skull. Of the size and general proportions of Sitomys gilberti, or of small 

 specimens of S. calif ornicus , except that the auditory bulke are markedly 

 smaller, being scarcely larger than in average specimens of S. a. gambelii, not- 

 withstanding the much larger size of the skull. In other respects there appear 

 to be no tangible cranial differences. Total length of the type (the other skull 

 is imperfect), 26 mm. ; basal length (posterior base of incisors to posterior border 

 of occipital condyle), 22 ; greatest width of brain-case, 12.5 ; least interorbital 

 breadth, 4.5 ; length of nasals, 10 ; length of lower jaw, 13.5 ; length of lower 

 jaw to tip of incisors, 16 ; height at coronoid process, 6. 



Type, No. 282, Mus. Leland Stanford University, Lakeport, Lake Co., Cal., 

 March 20, 1893 ; collector, S. Parrish. 



This species is based on two adult males, in the museum of the 

 Leland Stanford University, collected by Mr. S. Parrish at Lake- 



1 It is barely possible that the extreme tip of the tail in both specimens was mutilated in life, 

 but it seems by no means probable. 



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