1915.] Allen, Review of the South American Sciuride. 200 
presenting four distinct crenulations on the outer border; p‘ and m3 have 
the crown cup-shaped, the crenulations on the outer border obsolete. 
Geographic distribution.— The lower drainage areas of the Amazon and 
Orinoco rivers, the northern coast region of Brazil, and the forested parts 
of the Brazilian Highlands south to Parana and Sao Paulo. (See Map, p. 
301.) 3 
Remarks.— Guerlinguetus is most nearly related to M esosciurus, from 
which it is readily distinguishable by the possession of 8 mamme instead of 6, 
and by the much longer and narrower tail. In the general form of the skull 
and in the character of the dentition there is no very marked difference. The 
nasals, however, are shorter, their length being about 82% of the interorbital 
breadth instead of from 94% or more as in Mesosciurus; the skull is also 
narrower in comparison with the length, but the difference, while fairly 
constant, is too slight to be very impressive when reduced to percentage. 
Guerlinguetus, as here restricted, comprises G. estuans and G. alphonsei 
with their respective subspecies, which constitute the typical section of the 
genus. G. wmgramz is aberrant, but is better referred here than to any of the 
other groups here recognized as generic. It differs from the typical forms 
in being distinctly larger, in the coarser, longer pelage, and somewhat in 
style of coloration. The skull is much narrower in proportion to the length, 
and the teeth differ markedly in respect to the shape and the character of the 
crown surface of m’, which has a high anterior conical cusp. (Cf. Plate XIII, 
Figs. 28, 24.) G. angrami differs also in the physical character of its habitat, 
its distribution comprising the mountainous parts of southeastern Brazil, 
in contrast with the excessively humid tropical forests of the Amazon and 
Orinoco. G. wmgramz could well be separated from the estuans-alphonser 
group as a separate subgenus of Guerlinguetus, on the basis of the above- 
stated differences. 
Species and Subspecies of Guerlinguetus, with type localities and statement 
of number of specuomens examined. 
Guerlinguetus estuans estuans (Linné). Guiana. Specimens examined, 
17. 
Guerlinguetus castuans gilvigularts (Wagner). Borba, Brazil. Speci- 
mens examined, 18. 
Guerlinguetus estuans macconnelli (Thomas). Near base of Mount 
Roraima, British Guiana. Specimens examined, 1, the type. 
Guerlinguetus estuans quelchii (Thomas). Kanucha Mountains, Brit- 
ish Guiana. Specimens examined, 5. 
Guerlinguetus estuans venustus subsp. nov. Southern base of Mount 
Duida, Venezuela. Specimens examined, 1. 
