246 EXPLORATION OF THE CANONS OF THE COLORADO. 
giving compiled indications only of several others. Woodhouse 'described a 
new species in 1853. Various naturalists of the Pacific Railroad Surveys 
furnished field -notes of observation, but their determinations, to state a well- 
known fact, were not upon their own authority. In fact, the -literature of the 
whole subject, so far as original work in determination of species is concerned, 
focuses only in two authors Richardson, 1829, and Baird, 1857. 
No species of Thomomys having apparently been described before 1829, 
the history of the genus may be considered to begin at that date. The emi 
nent author of the Fauna Boreali- Americana gave five species of "Geomys" 
and "Diplostoma." One of these is a true Geomys; the four remaining ones 
(douglasii, bulbivorum, talpoides, and umbrinus), to which a fifth (borealis) 
was subsequently added, are all Thomomys. These accounts of Richardson's 
remained for many years the principal, and, in some cases, the whole, source 
of what has been written upon the determination of species ; and they include 
every form of the genus known up to this date (every subsequent name pro 
posed having proven a synonym). I hardly know where to look for the 
parallel of this curious case. Two points strike one in reviewing Richardson's 
work : First, he had a wholly erroneous idea that there were two distinct 
genera, "Geomys" and "Diplostoma," in one of which the pouches, opening 
into the mouth, dangled naturally as sacks on each side, and in the other 
of which the pouches were as we know them to be. This radically wrong 
premise vitiated all his work, and led him to the length of describing one 
and the same species as "Geomys douglasii" and "Diplostoma bulbivorum." 
Secondly, the minute descriptions consist mainly of the repetition, under 
varying forms of expression, of generic characters, common^ of course, to all 
the species. When sifted of their generalities, there is very little left ; though, 
fortunately, such was this author's habitual accuracy, the residuum suffices, 
when coupled with the indications of locality, for the identification of all his 
species. 
As already stated, there was little real change in the state of the case 
from 1829 to 1857, when Professor Baird reviewed the subject, with consid 
erably more material and much more other information than Richardson 
appears to have possessed. " Diplostoma" had meanwhile been effectually 
disposed of; but to this author is due the credit of having first actually iden 
tified with specimens several of Richardson's species, which, though often 
