1915.] Allen, Review of the South American Sciuride. 260 
Mus.); Sao Joao, Rio Grande do Sul, 1 (Phila. Acad.); “Brazil,” 2 (Nat. 
Mus. 1, Am. Mus. 1). 
Remarks.— Guerlinguetus ingrami is not closely related to the G. estuans 
group, from which it differs markedly in the character of the pelage, in color- 
ation and in its much larger size. It has a superficial resemblance to Gray’s. 
Macroxus leucogaster in coloration and in character of pelage, but differs 
widely from it in the structure of the molar teeth, and in having 8 mamme 
instead of only 6. It is less nearly related to the “cuscinus” group. 
Genus Hadrosciurus gen. nov. 
Text Fig. 9 (p. 163); Plate XII, Figs. 4-6; Plate XIV, Figs.7, 8. 
Type, Sciurus flammifer ‘Thomas. 
Size large, tail very long and bushy, about 53% of the total length; 
general form strong and heavy; mamme, 8. 
Premolars, +. Skull moderately broad and heavy; rostrum short, with 
short broad nasals, their length about 20 % of the total length of the skull, 
and about 66 % of the interorbital breadth; dorsal outline flattened, nearly 
as in Urosciurus and Simosciurus; zygomatic arches convex, broadest 
opposite the postorbital processes; malar strongly developed, expanded 
at the middle to form a prominent superior process; dentition heavy, the 
molariform series broader and heavier than in any other South American 
squirrel; postorbital processes heavily developed. In general effect the 
skull is strong and massive, but its breadth is relatively less than in typical 
Scvurus. 
Geographic distribution.— Valley of the Orinoco near mouth of Rio Caura. 
Extent of range not known. (See Map, p. 300.) 
Remarks.— In external appearance Hadrosciwrus has a general resem- 
blance to Urosciurus, but the tail is heavier than in most of the species of 
that genus, in which respect it is only equalled in U. dwida. The essential 
cranial characters are the heavy ossification, the relatively great breadth 
of the zygomatic arches, and the broad heavy malar with its prominent 
superior process. It resembles Simosciurus in the shortness of the rostrum, 
but not in other general features. In cranial characters it contrasts strongly 
with the typical forms of Urosciurus. The usual crenulation of the outer 
crown border of the maxillary teeth is well indicated on m3 in unworn- 
teeth, except that the parastyle is feebly developed. 
Remarks.—'The only known representative of H adrosciurus is Scvurus 
flammifer Thomas, a striking species in its external features and well dis- 
tinguished from all its allies by cranial peculiarities. 
