132 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 97 
foot; cranially, by extremely large fenestrations of the mesopterygoid 
fossa, larger, more inflated bullae, elongated, rather than broad, ham- 
ular processes, broad jugal with a distinct spinous process, narrower 
basioccipital, and by the enamel pattern of the molariform teeth. 
Remarks.—Only the typical form of the species is known. Judged 
by the original description and remarks by Ellerman (1940, p. 117), 
P. vacillator is most probably either a race of canicollis or a very nearly 
related species. 
P. canicollis was based on specimens from Bonda, Santa Marta, 
Mamatoco, and other nearby localities ranging in altitude, according 
to Allen (op. cit.), from sea level to 500 feet. Specimens were taken 
by the writer in the heavy deciduous forest of the Rio Cesar and the 
Rio Guaimaral, a channel of the Cesar. They were taken also in a 
nearby savanna (Palmarito) and from an intermediate site (Aguas 
Verdes) between the savanna and the forest. These rats were most 
abundant under decaying logs in the forest, and in the thick, spiny 
brush bordering the grasslands. Additional specimens were taken in 
the semiarid grass and scrub country about the town of Villanueva 
and in the similarly deforested region of the Ciénaga de Gudjaro. All 
series agree closely with topotypes of canicollis. No other species of 
Proechimys was found in these localities. 
According to Herbert H. Smith (in Allen, 1904, p. 440), who collected 
the type series of P. guyannensis mincae and of P. canicollis, ‘‘the latter 
is the common rat below 1,000 feet; the former takes its place in open 
lands, dry forests and thickets from about 1,000 to about 2,500 feet; 
but it does not extend far into the true mountain forest. Some mincae 
are found nearly to sea level, and canicollis occurs, rarely to 2,000 feet.” 
All present specimens of canicollis from the department of Magdalena 
are from the lowland areas surrounding the Sierra Nevada de Santa 
Marta. In the mountain mass itself, only specimens of mincae were 
taken. Apparently the two species have different habitat preferences 
where Smith collected. 
Specimens examined.—A total of 111, all in the collection of the 
United States National Museum: Bonda, 7; Santa Marta, 1; Ciénaga 
de Gudjaro, Atléntico, 15 meters altitude, 13; Rio Guaimaral, Rio 
Cesar, 140 meters, 13; Aguas Verdes, near Rio Guaimaral, 26; 
Palmarito, near Aguas Blancas and Rio Guaimaral, 3; El Orinoco, 
Rio Cesar, 158 meters, 15; Villanueva, 274 meters, 33. 
PROECHIMYS GUYANNENSIS (E. Geoffroy) 
Mus guyannensis E. Grorrroy, Catalogue des mammiféres du Muséum National 
d’Histoire Naturelle, Paris, p. 194, 1803. 
Echimys cayennensis DesMAREsT, Nouv. Dict. Hist. Nat., ed. 2, vol. 10, p. 58, 1817 
Type locality —Cayenne, French Guiana. 
Distribution (of the species).—Tropical parts of South and Central 
America from Nicaragua to southern Brazil and Paraguay. 
