The late Pliocene or early Pleistocene continental deposits occurring
in southwestern Idaho have yielded scattered fossil mammalian
remains during the past forty years or more. However, with the
exception of beaver material described as Castor accessor by O. P. Hay
nothing has been recorded concerning the rodents from these beds.
That a diversified assemblage of types occurs in these later Cenozoic
sediments is clearly shown by collections procured in recent years in
the course of palaeontological explorations along the Snake River
near Grand View and Hagerman, Idaho.
The westerly of the two principal localities in this region of Idaho is
situated on the west side of the Snake River approximately thirteen
miles northwest of the town of Grand View. This site was investigated
by the California Institute of Technology. The Hagerman locality,
where extensive excavations were conducted by the United States
National Museum, is situated on the Snake River across from the town
of Hagerman. In an airline, the distance between the localities at
Grand View and Hagerman is approximately sixty miles.
The United States National Museum has generously permitted me
to borrow the rodent collections obtained by that institution at the
Hagerman locality. The beaver remains were not included, since
important studies of this group are being conducted elsewhere. The
present paper embraces therefore a study of the rodent types now
known from the Hagerman and Grand View localities, with the exception
of the material noted above, and grateful acknowledgment
is made here for opportunity to study the National Museum collections.
Recent comparative material was loaned by the Division of Vertebrate
Zoology, California Institute. The illustrations of the rodent material
were prepared from photographic enlargements by John L. Ridgway.
The author also wishes to thank Dr. Chester Stock for opportunity to
study the California Institute collections and for supervision of the
work, as well as for a critical reading of the manuscript