RECENT LITERATURE 
265 
The apparent effect of climate upon the color and texture of the pelage in kan- 
garoo rats is pointed out, closely paralleling the findings of revisers of other groups 
of rodents with geographic ranges embracing both the humid Pacific coast region 
and the arid interior. Examples of nearly parallel conditions are found in the 
wood rats — Neotoma intermedia intermedia of the western slope of the mountains, 
and Neotoma intermedia desertorum of southeastern California ; and Neotoma cinerea 
cinerea typical of the Great Basin and its darker coastal counterparts Neotoma 
cinerea occidentalis and Neotoma cinerea fusca^ and in others which may be readily 
cited. 
Consideration of habitats, says the author, ‘‘in connection with size of ear 
brings out unmistakably the correlation of small pinna with open type of habitat, 
and in the other direction, of large pinna with a chaparral type of habitat. 
The same tendencies are to be observed in Peromyscus and Perognathus.” While 
this may appear to be true in some of the California forms of these genera, it 
should be noted that the kangaroo rats with the largest and the smallest ears, 
Dipodomys elephantinus and Dipodomys microps, are assigned habitats as species 
wholly within chaparral, and more open types of country, respectively. The 
large-eared California pocket mouse, Perognathusfemoralis, which the author may 
have in mind, is another chaparral-loving species with a very restricted known 
range. Some species of Peromyscus and of mammals in general inhabiting open 
types of country have very large ears. Admitting that certain large-eared species 
of kangaroo rats are associated in California with more brushy habitats than are 
usual in the general group, such generalizations would seem better based upon 
studies of more widely ranging species subdividing into geographic races and 
inhabiting cover of varying density. 
In the discussion of distributional considerations the conclusion is reached that 
“as regards the species and subspecies of kangaroo rats in California, humidity 
is of minor importance as a barrier to extension of range as compared with unfa- 
vorable temperature and bodies or streams of water.” The probable evolution of 
ranges is traced. Owing to the aversion of Dipodomys for water, continuous 
bodies of this element are regarded as effective barriers, but Dipodomys deserti 
and Dipodomys merriami occur on both sides of the lower Colorado River where 
shifting river channels transferring tracts of inhabited bottom land from one side 
to the other have doubtless given access to the opposite side. The transference 
of individuals, postulated by the author, would be especially likely to occur 
during such extensive changes in the course of the stream as took place fifteen 
years ago, when through the agency of man in cutting a narrow irrigation ditch, 
the great river was unintentionally turned into Salton Sea whence it was rediverted 
with the greatest difficulty at the end of about a year; and the course taken by 
the main stream since this diversion is in places many miles west of that formerly 
followed. 
In the formal treatment of species there are no generalized accounts of species 
as aggregations of subspecies, the author passing directly to a consideration of the 
component parts. The first species receiving attention is Dipodomys heermanni, 
and in treating its parts, instead of following a common custom among revisers 
of taking up first the typical subspecies, he begins with the widely ranging 
northern form, Dipodomys h. californicus, and proceeds southward, the typical 
form being third in the series . On reaching Dipodomys agilis, however, the typical 
