Mr. O. Thomas on the Echimyine. 295 
The spineless species with complicated Echimys-like teeth 
may be retained as a distinet genus, Jsothrix, with type 
I. bistriata, and other species villosa (which perhaps= 
bistriata), orinoct, picta, and pagura [I. pachyura, Wagn., 
renamed later J. crassicaudus, was said to be probably the 
same as Lund’s Nelomys antricola, which is a Cercomys]. 
At the same time, it may be observed that there appears 
to be no constant difference in skull or dentition between 
Echimys and Isothrix, though the marked distinction in the 
characters of the coat justifies the retention of the genus 
Lsothrix, with which Lasturomys is synonymous. 
Of the type-species of Echimys, E. chrysurus, Zimm., of 
Guiana, the Museum possesses examples from the Upper 
Corentyn (Sir R. Schomburgk), R. Supinaam (Ff. V. McCon- 
nell), and Potaro Highlands (Dr. C. Bovallius), while a skin 
of the closely allied but smaller Amazonian species H. palea- 
ceus, Licht., has been received from the Goeldi Museum, Para 
(locality, Peixe Boi), as also have two specimens of the 
“Toro”? of the Lower Amazons, Lchimys grandis, Wagn. 
(Santarem and Faro). 
The other Guiana species, which was described by me in 
1888 as Loncheres guiane, is unquestionably LE. armatus, 
Geoff., whose determination has been long in doubt, but 
whose locality (Cayenne) and external characters, as shown 
in Lichtenstein’s figure, absolutely agree with those of 
L. guiane, with which ZL. castaneus, Allen, is also synony- 
mous. ‘The species ranges from Trinidad and the mainland 
opposite eastwards to Cayenne, and also occurs on the Lower 
Amazon (Para, Cametdé) and in Northern Maranhao (Miri- 
tiba). It is exceedingly variable in coloration, as is shown 
by our considerable series from British Guiana, where it is 
very common. 
Finally, the three closely related species semivillosus, punc- 
tatus, and carrikeri occur in Eastern Colombia and Venezuela, 
but material does not exist for their proper comparison with 
each other. 
In Nelomys (syn. Phyllomys) the upper molars consist of 
four simple transverse lamin, which persist without 
coalescing with each other at different ages, this continued 
separation being due to the equal depth of the three trans- 
verse valleys dividing the lamin. In Hehimys and Isothria, 
owing to the varying depth of the valleys, the laminze 
coalesce and present a more complicated pattern, which 
varies at different ages. 
Of Nelomys blainvillei, Jourdan, the genotype, the Museum 
possesses one of the original specimens collected on the Isla 
20* 
