208 Bulletin American Museum of Natural History. [Vol. XXXIV, 
Oct. 8, 1904 (Suapuré, La Union, and El Llagual, Venezuela); ibid., XXVIII, p. 146, 
May 27, 1910 (Rio Mocho, Venezuela). | 
Sciurus (Guerlinguetus) estuans gilvigularis ALLEN, Bull. Amer. Mus. Nat. Hist., 
XXX, p. 255, Dec. 2, 1911 (Rio Mocho). 
Sciurus estuans gilvigularis THomas, Ann. and Mag. Nat. Hist. (8), XI, p. 87, 
Jan. 1912. Faro, near mouth of Rio Yamund4, Lower Amazon. 
L'ype locahity.— Borba, Brazil, near mouth of Rio Madeira. 
Geographic description.— Amazonas, from near the mouth of the Rio 
Madeira westward to an unknown distance, and the valley of the middle 
portion of the Rio Orinoco; probably also the drainage areas of the Rio 
Branco and Rio Negro. 
Deseription.— Pelage short and thin, very close and short on the feet 
and ears. Similar in general coloration to Guerlinguetus estuans estuans 
but paler and rather smaller, with a narrower tail. Upperparts finely 
grizzled light ochraceous buff (Ridgway) and black; eye-ring narrow, pale 
buff; underparts dark ochraceous orange, most intense on the chest and 
upper abdomen, somewhat paler posteriorly and much paler on throat; 
limbs externally like the dorsal surface, internally like the ventral surface; 
tail above coarsely grizzled with buff and black and broadly edged with 
buff, varying in intensity in different specimens; underside of tail with the 
median area finely grizzled with buff and black, the hairs with a broad 
subapical zone of black, edged with a broad fringe of buff. 
The above description is based on 6 specimens from the type region, 
including specimens from Santarem, Obidos, and the lower Rio Yamundé. 
A series of specimens from the Rio Caura and middle Orinoco region are 
similar. en 
Total length, adult male, 337 mm.; head and body, 166; tail vertebree, 
167; hind foot, c. u., 45. Five specimens from the lower Rio Caura, total. 
length, 342 (329-357); head and body, 169 (155-177); tail vertebra, 173 
(165-178); hind foot, 45 (43-47). 
Five skulls (lower Rio Caura yegion), total length, .44.4 (43.5-47); 
zygomatic breadth, 25.4 (25-26); interorbital breadth, 14.6 (13.3-15.3); 
breadth of braincase, 20 (19-21); length of nasals, 12.7 (12-13.5); dias- 
tema, 11.1 (11-11.5); maxillary toothrow, 7 (6.4-8). | 
Specumens examined, 18.— Brazil: Santarem, 3 (Am. Mus. 2, Mus. 
Comp. Zool. 1); Obidos, 4 (Mus. Comp. Zool.); Faro, Rio Yamunda, 3 (Field 
Mus. 1, Am. Mus.-2). , 
Venezuela: Suapure, Rio Caura, 5 ; Rio Mocho, 1; La Union, 1;: El 
Lagual, 1 (all in Am. Mus.). 
Remarks.— Wagner in his later full description of Sciwrus gilvigularis 
(7. c., 1850) made his comparison of gilvigularis with what is now known as 
