[ 35 
VI. On the Chinchillide, «@ Family of Herbivorous Rodentia, and on a new Genus 
referrible to it. By E. T. Bennerr, Esq. F.L.S., Sec. Z.8. 
Communicated May 14, 1833. 
IN the well-defined division of the purely Herbivorous Rodentia, characterized by the 
want of distinct roots to their molar teeth, which are continually growing by the ad- 
dition of fresh matter to their base as their crown is worn away by attrition, the little 
family which I propose to designate Chinchillide is deserving of peculiar attention. 
This family (which may at once be distinguished by its teeth, consisting of either two 
or three parallel and ribband-like bony /amelle, each surrounded by its own proper 
coat of enamel, and connected to its neighbour by the intervention of cortical substance 
alone,) consists at present of two genera, both established within the last five years, 
Lagostomus and Chinchilla. Of the former, one species only, the Viscacha of the plains 
of Buenos Ayres, has been described. Of the latter, besides the Chinchilla, long popu- 
larly known for the extreme fineness and beauty of its fur, and of late scientifically de- 
scribed by various writers, there appears to exist a second species, the mutilated skins 
of which have not yet afforded sufficient materials for its complete definition. To these 
I have now to add a third genus; which I have no hesitation in regarding as new to 
science, although, if my conjecture as to the origin of the animal be correct, it has 
been repeatedly noticed by travellers for a period of nearly three hundred years. 
In describing, after D’Azara, the Viscacha of the Pampas of Buenos Ayres and Para- 
guay, M. Desmarest! refers to an unpublished drawing by Feuillée of a Viscacha ob- 
served by that author in Peru, and suggests the probability of its belonging to a distinct 
species. A careful comparison of the scattered notices published by travellers and 
naturalists of the Viscachas of the Eastern and Western sides of the Andes, had long 
since led me to form a similar opinion as to their distinctness. This opinion was fully 
confirmed on the acquisition by the Society, in the month of June last, of a living 
animal, obviously nearly allied to the Viscacha of Buenos Ayres, but possessing the 
distinguishing peculiarities of the Peruvian species ; and which consequently, although 
no information could be obtained as to its native country, I did not hesitate to refer to 
that obscure but highly interesting form. At the next Meeting of the Committee of 
Science and Correspondence I made some remarks on its affinities, pointing out various 
external characters by which it was distinguished from both Chinchilla and Lagostomus, 
the only two genera with which it appears to come into immediate contact; and inti- 
mated my intention of establishing on it, whenever its death might furnish the oppor- 
' Mammalogie, p. 360, note. 
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