1915.] Allen, Review of the South American Sciuride. 219 
Subspecies hof'manni, as at present known, presents an unusual case of 
discontinuous distribution among the smaller mammals, since it has thus 
far not been found in any part of northwestern Colombia. The mammal 
fauna of the Panama region is now fairly well known, and considerable 
collections of squirrels are available from the adjoining parts of Colombia 
and the coast of western Colombia, which regions, however, have not thus 
far furnished a single specimen related in any way to hof'manni. Aside 
from several forms of Microsciwrus, this non-hoffmanni region is occupied 
exclusively by the Sciwrus gerrardi group of much larger and widely different 
squirrels; and from no point thus far have specimens of both the gerrardi 
and hoffmanni groups been received. In Colombia hoffmanni is absent from 
most of the western slope of the Western Andes, where it ranges from about 
3000 to 8000 feet; but it has a closely related geographic representative 
in the low coast region of Ecuador, just as it has at low levels in Chiriqui 
and Costa Rica. The hoffmanni group ranges eastward from the Central 
Andes into the northern Eastern Andes to the Bogota district, where it 
breaks up into several closely related local forms, some of which may be 
found later to merge into the griseogena group of the Sierra Merida and 
Codillera de la Silla of Venezuela; but such intergradation seems not as 
yet fully evident. 
The wide hiatus in the present known range of the hoffmanni group at 
Panama and adjoining Colombian districts presents an interesting and 
difficult problem. Possibly its larger and probably aggressive neighbors 
of the gerrardi group have driven it out of their present range to the higher 
levels they do not affect. On the other hand it may more probably be due 
to long past geologic disturbances in the Isthmian area. 
Mesosciurus richmondi (Nelson), of northeastern Nicaragua and Hon- 
duras, is an outlying and the most northern member of the Mesosciurus 
group, allied to but quite distinct from hoffmannt, and separated from it. by a 
considerable geographical area where neither species occurs, hoffmanni not 
extending, so far as known, north of Costa Rica. 
Sciurus hof'manni séderstrémi Stone (I. c.) was based on a skin (without 
skull or measurements) from “ Mt. Pichincha,” collected by L. Séderstrom, 
and is thus described: “While a member of the S. hof'manni group, this 
specimen is much more rusty-red, especially across the shoulders and on 
the fore legs, than any specimens I have seen from Costa Rica or any in a 
eS 
———. 
1 Sciurus richmondi Newson, Proc. Biol. Soc. Washington, XII, p. 146, June 3, 1898 
(Escondido River, Nicaragua); Proc. Washington Acad. Sci., yes 100, 9, 1899.— 
AuuEn, Bull. Amer. Mus. Nat. Hist., X XIV, p. 660, Oct. 13, 1908 ( icaragua, : 
Sciurus (Guerlinguetus) richmondi ALLEN, Bull. Amer. Mus. Nat. Hist., XXVIII, p. 104, 
April 30, 1910 (Nicaragua). 
