130 Mevrlam — New Ground Sqiilrreh. 



Color. — Up])er parts dull yellowLsli-ln'owu or buffy clay-color, 

 which color covers the outer surfaces of the legs and the prox- 

 imal third of the U[)per side of the tail ; a white stripe on each 

 side reaching from l)ehind shoulder to rump; under parts, feet, 

 and eyelids soiled whitish, the feet more or less strongly suf- 

 fused with bufify. Tail above : proximal third buffy clay-color 

 like back ; distal two-thirds mixed black and -whitish with a 

 whitish border; tail below : soiled or buffy whitish, bordered 

 on distal two.-thirds with a broad subterminal l)lack band, and 

 edged with whitish. There is also a very narrow black zone at 

 the base of the tail hairs. The upper parts are rather coarsely 

 lined with black hairs which are absent from the legs, giving the 

 latter a slightly different tint, and in some specimens the ground 

 color of the legs and sides just above the forelegs is diflferent, 

 being suffused with dull buffy ochraceous. The fall and winter 

 pelage is darker and softer than the summer pelage. 



Cranial Characfers. — Skull similar to that of S. lencnrnx, but 

 larger and broader; audital bulla' conspicuously larger, more 

 inflated and distinctl)^ corrugated. The corrugations are due to 

 the presence of two transverse constrictions, marking the posi- 

 tion of vascular canals ; the}' are faint or absent in leucurusjiar- 

 risi, and the other pre\'iously described forms. The rostrum 

 and nasal bones are somewhat longer, and the upper incisors 

 and first upper premolar are larger than in leucuras. 



Specimens Examined (all from San Joaquin Valley, California). — 

 Total number, 52, from the following localities : Tipton (t3'pe 

 locality), 32 ; Huron,?; Adobe Station, 1; Alila, 2; Lerdo, 2 ; 

 Poso, 3; Temploa Mountains, 2; Lake Buena Vista, 3. 



General Remarks. — The difference between Amm-ospermopJiilus 

 nelsoni and the previously known members of the group is much 

 more decided than between any of the others. The animal is 

 larger, paler, and very different in color, the upper parts being 

 everywhere from nose to tail a uniform dull yellowish or 1)uffy 

 clay-color, rather coarsel}^ lined with black hairs. The cranial 

 peculiarities have been already described. The fall molt evi- 

 dently takes place early and progresses from behind ft)rward, as 

 shown by the 13 specimens collected by Mr. Nelson in October. 

 All of these liave completed or nearlv com})leted the change, 

 the only old hairs remaining being on the head and belly. In 

 some of the specimens from Poso the pale, l)uffy clay-color of 

 the head, still in worn summer iielage, is in striking contrast 



