On the Classification of the Cavies. 301 
Within Huryzygomatomys I now find it possible to distin- 
guish from the true Paraguayan spdnosus the form found in 
Santa Catherina as follows :— 
Euryzygomatomys catellus, sp. n. 
General colour and other external characters as in FZ, spi- 
mosus, except that on the under surface the white area is 
much reduced in extent. In spinosus the whole under surface 
from chin to inguinal region is white, and this colour extends 
nearly or quite over the whole breadth of the belly, where it 
grades, without very sharp line ef demarcation, into the buffy 
or drab of the flanks. In FE. catellus, on the other hand, the 
chin and throat are suffused with brownish, there is a marked 
brown patch in the middle of the chest, and the white of the 
belly is reduced to a comparatively narrow median area owing 
to the encroachment on it of the brownish or drabby flank- 
colour, from which its line of demarcation is somewhat 
abruptly defined. 
The skull is, on the whole, similar to that of JH. spinosus, 
except that the V of the palatal notch is less excessively 
narrow and pointed, and does not extend quite so far into the 
palate—at most to the posterior third of m?, and more often 
only to the hinder edge of that tooth. 
Dimensions of the type (measured on the spirit-speci- 
men before skinning) :— 
Head and body 245 mm. ; tail 53; hind foot 35; ear 18. 
Skull: greatest length 49; condylo-incisive length 46°2 ; 
zygomatic breadth 27°3; nasals 14°3x6°5; interorbital 
breadth 11; palatilar length 19°2; upper tooth-series 10. 
Hab. Santa Catherina. Type from Joinville. 
Type. Adult male. B.M. no. 9.11.19. 30. Collected 
by W. Ehrhardt. Four specimens. 
I have provisionally used a binomial name for this animal ; 
but intermediate forms may prove to exist in the little-known 
country between its type-locality and that of EH. spinosus, 
and it will then have to be regarded as a subspecies. 
XXXIV.—On the Classification of the Cavies. 
By Ouprietp THomas. 
(Published by permission of the Trustees of the British Museum.) 
Mr. Witrrep Oscoop has recently published a suggested 
revision of the classification of the Cavies*, and has divided 
* Field Museum Publ, Zool. x. p. 194 (1915), 
