By Dr. J. GRINNELL. 
California Museum of Vertebrate Zoology. 
In traversing the southern road, from San Diego past Mountain 
Spring, the single feature of greatest interest to me pertained to topog- 
raphy. Having never been through that country before, my notions of 
it had been derived from brief references to it in literature, and I had 
imagined ‘‘the coast ranges’’ to consist of a series of narrow ridges 
parallel to one another and with intervening canyons. It was a sur- 
prise, therefore, for me to find that, instead, the elevated tract, extend- 
ing from the top of the Potrero grade to the edge of the abrupt desert 
dechvity above Mountain Spring, is a plateau. As pointed out by 
Mr. Stephens the surface of this plateau is rolling, reminding me of 
the peneplain country in parts of New England. The drainage is slow 
and the transition from the evident north-and-south line of greatest 
rainfall, in the vicinity of Campo, to the edge of the Colorado Desert, 
thirty or forty miles beyond, is gradual. 
The effects of these topographic peculiarities upon the flora and 
fauna are such as to bring, not an abrupt change from Pacific coast 
conditions to those of the Colorado Desert, but a gradual blending, be- 
ginning near Campo and still in evidence at the edge of the plateau 
above Mountain Spring. It was with extreme interest that I noted the 
disappearance here and there of Pacific coast plants and the coming in 
of successively more xerophilous species. With very little doubt the 
behavior of the birds, mammals and reptiles accords in general with 
that of the plants, and I could only wish for the opportunity to hunt 
and trap throughout the entire section, and thereby determine the facts. 
The few species seen in our rapid transit did not happen to be of eriti- 
cal sorts. 
Historically, the line of our trip passed several points of special 
interest to the student of systematic mammalogy, namely the type lo- 
calities of a number of species. I was greatly interested in seeing the 
kind of ground where Mearns secured the specimens from which he 
described his several new forms: Peromyscus crinitus stephensi, Perog- 
natus fallax pallidus, and Lepus califormcus deserticola—in the vicinity 
of Mountain Spring and where the topotypes of Peromyscus ceremicus 
fraterculus, Peromyscus californicus insignis, Perodipus streatori sim- 
ulans and Perognathus californicus femoralis were obtained—on a 
brushy mountain side near Dulzura. Since the environment prescribes 
in large measure the characters of a species, one can never expect to 
