132 GLIRES. 
while others from Brazil are under 10 inches, although evidently adult. Nor is it 
constantly connected with any of the numerous varieties of coloration—rufous, grizzled, 
and melanistic specimens occurring of all sizes. In this case, also, Mr. Allen has fully 
accepted my determination °. . 
S. variabilis appears merely to enter the most southern portion of our subregion ; 
the Museum of Comparative Zoology at Cambridge, Massachusetts, has received speci- 
mens from Panama collected by Dr. Maack and by the Hassler Expedition ®; and there 
are others, obtained in the same State by M. Boucard, in the Paris Museum. I have 
been unable to trace it further north. 
7. Sciurus estuans. (Sciurus griseogenys, Tab. XIII.) 
Sciurus estuans, Linnzus, Syst. Nat. i. p. 88 (1766, descr. orig.)*. 
Sciurus estuans, var. hoffmanni, Peters, Monatsb. Ak. Berl. 1863, p. 654 (descr. orig.)?; Frantzius, 
Arch. f. Naturg. xxxv. 1, p. 267°. 
Sciurus estuans, var. rufo-niger, Allen, Mon. N.-Am. Rodent. p. 757 (nec S. rufo-niger, Pucheran)*. 
Sciurus hoffmanni, Allen, Bull. U.S. Geol. Surv. iv. p. 885 (1878, ex Peters)*. 
Macroxus zanthotus, Gray, Aun. & Mag. Nat. Hist. 3rd ser. xx. p. 429 (1867, descr. orig.)°. 
Macroxus griseogena, Gray, loc. cit. (1867, descr. orig.)’. 
Sciurus griseogenys, Alston, P. Z.S. 1878, p. 667°. 
Hab. Nicaracua (Mus. Berol.); Costa Rica (Hoffmann, Mus. Berol.2; Frantzius ie 
Volcan de Cartago (Arcé, Mus. Brit.); Panama, Calevevora (Arcé, Mus. Brit.: 
Boucard, Mus. Paris.)—Souta America to Brazil and Bolivia. 
There are two marked geographical races of this well-known Neotropical species, and 
some confusion has arisen as to their relationship and nomenclature. The northern 
form, ranging from Nicaragua to Ecuador, is distinguished by its large size and its 
bright red belly and tail, and was first described as a variety by Professor Peters2. It 
subsequently became the ground of several of Gray’s nominal species, and was then 
identified by Mr. Allen with the Sciwrus rufo-niger of Pucheran4. In my review of 
the Neotropical Squirrels I was enabled to show that this was an error; and although 
expressing my belief that the races would yet be found to intergrade, I felt compelled 
in the absence of intermediate specimens to separate the northern variety provisionally 
under Gray’s name of S. griseogenys*. Mr. Allen followed the example, but preferred 
to raise Dr. Peters’s varietal title of hoffmanni to specific value®, Since then, however, 
my friend Mr. Oldfield Thomas has described complete connecting links, which he finds 
in specimens from Ecuador, exactly the locality from which they might be expected, 
as it is there that the Andean and Amazonian races meet *. Mr. Allen and Lare there- 
* P.Z.S8. 1880, pt. ii. (in the press). 
