SQUIRRELS OF MEXICO AND CENTRAL AMERICA 3 1 



bushy, flattened ; color usually some shade of brown on upperparts 

 and buffy or rufous below. 



Cranial characters. — Premolars \. Skull rather broad, flattened 

 interorbitally ; rostrum broad and deep at base ; nasals long, ex- 

 panded at outer end ; braincase not very highly arched but expanded 

 laterally over parietal region ; audital bullas small ; post-palatal notch 

 a little farther behind last molar than in Microsciurus (about as in 

 Baioschirus') ; palatal width between molar series great. The skull 

 resembles in size and general appearance that of Bawschirzis, from 

 which it is distinguishable by slender rostrum, proportionately greater 

 interorbital and zygomatic breadth, and by the absence of the small 

 premolar. 



General itotes. — Gucrling-uetus, proposed by Gray in 182 1, is the 

 first name available for a subgenus of American squirrels. It was 

 subsequently discarded by its author for Macroxus, proposed two 

 years later by Cuvier in the ' Dents des Mammiferes.' In the ' Nom- 

 enclator Zoologicus,' Agassiz cites Macroxus from the ' Dictionnaire 

 des Sciences Naturelles, X, 1S18,' but a careful search fails to verify 

 the reference. The name does appear in the Dictionnaire Classique 

 d'Histoire Naturelle, Vol. X, 1826, p. 16, which was probably the cita- 

 tion intended by Agassiz. The ' Dents des Mammiferes' was completed 

 in 1S25, but on page xvi of the introduction Cuvier states that the 

 work appeared in parts, and that the part containing the rodents was 

 issued in 1823; from which therefore must date Macroxus. Subse- 

 quent writers have followed Gray in ignoring Guerlinguetus in favor 

 of Macroxtis. The latter name was proposed for the group typified 

 by Sciurus cestuans of South America, yet Lesson in 1842, Gray 

 in 1867, and Trouessart in 1880 and 1897, included under it the 

 most diverse squirrels in America. Guerlinguetus should be strictly 

 limited to S. cestuans with its numerous subspecies and allies, all of 

 which have brownish backs with brown, fulvous, or rufous bellies and 

 a single upper premolar. It is a characteristic group of northern 

 South America, intrusive in Central America where it is represented 

 by S. a. ho^manni of Costa Rica and S. richmondi of Nicaragua. 



BAIOSCIURUS' subgen. nov. (p1. I, fig. 4.) 



Type Sciurus deppei Peters, from Papantla, Vera Cruz. 



Distribution. — Northeastern Honduras, Guatemala, Chiapas and 

 eastern Mexico to Tamaulipas. 



' From (iaioc, small ; -f Sciurus. 

 Proc. Wash. Acad. Sci., May, 1899. 



