SQUIRRELS OF MEXICO AND CENTRAL AMERICA 7 1 



Color. — Upperparts, including feet, rather coarsely grizzled black 

 and gray (sometimes suffused with yellowish), more yellowish along 

 middle of back and paler gray on sides of nose, body, and feet; ring 

 around eye dingy whitish ; ears sometimes dark gray and sometimes 

 with distinct dingy white basal patch and small dull yellowish white 

 tuft at tip S or 9 mm. long; underparts varying from white to pale 

 grizzled gray. Tail at base similar to back; rest of tail above black, 

 heavily washed with white ; below, with median area coarsely grizzled 

 black and gray, or dull, pale fulvous, bordered by black and edged with 

 white. Hairs on back black, with broad median ring of white or 

 yellowish. 



Variatioji. — The small series examined does not show much sea- 

 sonal difference, but the presence of ear patches and small tufts in two 

 specimens ( $ and 9 ) and their absence in three others indicate the 

 probable existence of certain marked differences of this kind. One 

 specimen taken at Chichenitza (Mar. 7) is mainly iron gray with slight 

 trace of yellow on the back; the underparts are whitish finely grizzled 

 with black. Another specimen taken at the same locality (Mar. 18) 

 has a strong yellowish shade on the upperparts, and the chin, neck, 

 breast, and middle of belly are nearly pure white, the underparts being 

 grizzled with black only along border of flanks. 



Measurements. — Average of two adults from Chichen-Itza : total 

 length 451 ; tail vertebrae 222 ; hind foot 55. 



Cranial characters. — Premolars \. Skull very similar in general 

 outline to that of typical S. aureogaster but much smaller, with pro- 

 portionately longer nasals and larger audital bullae; nasals rounded in 

 front as in aureogaster. The single skull at hand shows no approach 

 to the massive rostrum and broad flattened nasals of the thomasi 

 group. It measures: basal length 45; palatal length 23; interorbital 

 breadth 16.2; zygomatic breadth 19; length of upper molar series 9.5. 



General notes. — Sciurus yucatanensis is at once separable from 

 S. carolinensis and its races, and from S. alleni.^ by the much coarser 

 grizzling on the back, and the stiffer, harsher pelage in addition to the 

 cranial characters. It is a strongly marked species, the presence of 

 whitish ear tufts in certain pelages separating it from the other Mexi- 

 can and Central American squirrels of the subgenus EcJiinosciurus. 



Specimens examined. — Five : from Merida and Chichen-Itza, Yuca- 

 tan. 



SCIURUS THOMASI sp. nov. Costa Rica Squirrel. 



Sciurus boothics Allen, Men. N. Am. Rodentia, pp. 741-746, 1877 (part : 

 specimens from eastern Costa Rica. — Not S. boothia Gray, 1842). 



