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 bullce small ; post-palatal notch 

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

 Baiosciurus^ ; palatal width between molar series great. The skull 

 resembles in size and general appearance that of Baioscittrus^ from 

 which it is distinguishable by slender rostrum, proportionately greater 

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

 premolar. 



General notes. — Guerlinguetus., 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 Alacroxus., 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'HistoireNaturelle, Vol. X, 1S26, p. 16, which was probably the cita- 

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

 in 1825, 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 1S23 ; from which therefore must date Macroxus. Subse- 

 quent writers have followed Gray in ignoring Guerlinguetus in favor 

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

 by Sciurus cestuans of South America, yet Lesson in 1S42, Gray 

 in 1S67, and Trouessart in 1880 and 1897, included under it the 

 most diverse squirrels in America. Guerlinguetus should be strictly 

 limited to 6". 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. hofftnanni 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 [iai6r, small ; + Scinrus. 

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



