('.70 



MONOOIlAPna OP north AMEIIHIAN RODHNTfA. 



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of note tlint the smullest species {Sciurus hudsoniua) is the most northern, 

 nnd thnt the next Bmullest (Sciurus aaluans) is tlic most Bouthem, both 

 occurring on the extreme lioundnries of the hnhitat of the group. These 

 ((gain, ill respect to the development of the tail, arc the least Sciurine; the 

 long, full, bushy, distichous tail, so characteristic a feature of the Sciuri as 

 distinguishing them from their allies, being in these two species very much 

 sliorter and narrower than in any of the others. In passing southward, wu 

 meet, next after S. hucfsanius, with S, carolinensis, a species again below the 

 average in size, with the tail only moderately developed, although there are 

 .xonie Mexican an<l Central American species equally small. The largest 

 species, as well as the greatest number, and those with the largest tails, are 

 Mexican; Western and Southern Mexico being apparently the centre of devel- 

 opment, or metropolis of the group, as respects the two Americas. None are 

 thus far known from any of the intertropical islan<ls. 



As already observed, the American Sciuri form a group so homogeneous 

 as not to be readily subdivisible. Taking, however, the relative length of the 

 tail, and the number and character of the upper premolars, as a basis, with such 

 otiier features as are most readily available, the species and subspecies may 

 be conveniently (and somewhat naturally) grouped as follows : — 



SYNOPSIS OF THE SPECIES AND SUBSPECIES OF AMERICAN SCIURI. 



I. Tail very short and narrow, the oandal vertebric alone about two-thirds as long as the haad and boiljr ; 

 tail to end of hairs about one-seventh shorter than the bead and body ; premolars f , the 

 first very small nnd often decidnoas; u narrow, black, lateral line; size sBiall. Ote 



* . species with fonr subspecies : 



1. Above fprayish, mixed with yellowish or reddish, annulale<l with dusky, often with a strong 

 wash of ferrnginons along the middle of the back ; below generally white, Mnnetimes 

 narrowly annnlated with black ; in one subspecies fulvous below. Hafr.— Northern half 

 of North America 8. nciwoNirs. 



a. Above yellowish-gray, varied with black, with generally the middle of the back strongly 



washed with ferruginous ; npper surface of the tail with the hairs rasty at the base and 

 reddish-tipped, with a broad subterminal bar of black. Bab. — Norlbem North America 

 east of the Rocky Mountains and northwestward to Alaska var. t«<boafa>. 



b. Above varied with black and yellowisb-rasty ; upper surface of the tail with (he hairs gray 



at the base and gray-tipped, with a brood subterminal bar of black. Bab. — Central portion 

 of the Rocky Mountains, and thence westward to the Sierra Nevadas vsr. fremmll. 



e. Almve dnsky, strongly varied with reddish ; npper surface of the tail with the hairs dark 

 reddish-brown at the base, tipped with reddish, and with a very brood subterminal 

 bar of black, sometimes occupying the whole of tlie terminal third. Bat.— Rocky 

 Mountains between latitude 43° and 68", and thence westward to the Cascade 

 Range vir. rtebardimi. 



d. Above as in the prrceding (vor. HcAariiiHwi); tail wiCi Ivm black; beneath moreorlena 

 strongly tinged with fulvonsor rnfons. tftft.— Paciflc-cnast region from Northrro Ciili- 

 foruia to Sitkn ywc. toutlmti. 



