COUES ON GEOMYS AND THOMOMYS. 245 
Not to pursue this subject to the extent of further allusion to laws fairly 
deducible from such premises, it is a logical inference from what has been 
said that there is but one "species" among all these specimens. This "species" 
is modified by some unknown means, evidently related in some way to the 
climate, soil, vegetable productions, or other peculiarities of certain geo 
graphical areas, yet not to the extent of severing the links which bind all its 
individuals together. This species, in the course of time, by the continued 
operation of the same influences, may or may not be resolved into three or 
more species in the current acceptation of the term ; but at present such is 
not the case. It is my intention, in the following pages, to describe these 
variations in detail. In so doing, I consider it advisable, for convenience' 
sake, to give them each a name ; and, in so doing, I shall adopt a formula 
of nomenclature which I consider best suited to suggest the intergradation 
which I find to exist, without reference to Linnaeus or to the British Asso 
ciation. 
It may tend to take the edge off the imputation implied in the remark 
made above, that six or eight species admitted by naturalists of high repute 
must be reduced to one, to briefly review the written history of Thomomys. 
The literature of the subject is unusually brief, and it is somewhat surprising 
how much of it is pure compilation, which has no actual bearing upon the 
case. Eydoux and Gervais, and Maximilian, each described a species, and 
Waterhouse and Brandt have both handled the general aspects of the case ; 
but, with these exceptions, almost no original work appears from foreign 
authorities. Fischer, Schinz (whose one new species was a self-confessed 
synonym), Wagner, Giebel, and doubtless other systernatists, have treated 
of a number of species of Thomomys, but entirely at second hand. Such 
authorities may be passed over in respectful silence, having no weight 
whatever. The very slight knowledge from abroad will seem the less 
remarkable when we find how little has been done by the naturalists of this 
country. Rafinesque's animals appear to have been all Geomys. Godman 
had nothing to say upon the subject. Bachman's descriptions of two species, 
in 1839, were upon Richardson's MSS. DeKay enumerated some species 
at second hand. Audubon and Bachman's accounts of several species add 
positively nothing to what was already extant upon the subject. When 
LeConte monographed the family in 1852, he knew but a single species, 
