Vol. IX] TAYLOR— COOPER'S MAMMALS 77 



470; 1870a, p. 66; 1871b, p. 756). The expedition left Los 

 Angeles on December 4, 1860, arriving at the post two weeks 

 later on December 19. While stationed at Fort Mojave 

 Cooper undoubtedly collected on both sides of the Colorado 

 River, usually labelling the specimens gathered "Fort Mojave, 

 Col'do V." or "Fort Mojave, Col'do R." without distinction 

 as to state or territory. In a few cases records of species 

 actually collected or observed on the Arizona side only were 

 without doubt credited to California (see Cooper, 1890, p. 

 215). 



On May 28, 1861, Dr. Cooper started on his return journey 

 to the coast (Cooper, 1869, p. 480; 1870a, p. 66) which was 

 completed in approximately 14 days. May 29 found the 

 party in the Providence Mountains (Cooper, 1870c, p. 252) ; 

 on June 6 it had reached Camp Cady on the lower Mojave 

 River (a specimen of Peromyscus m. sonoriensis, No. 5625, 

 Univ. Calif. Mus. Vert. Zool, collected at this locality on June 

 6, is extant) ; on June 8 the expedition had arrived at the 

 headwaters of the Mojave River near Cajon Pass (Cooper, 

 1861, p. 123); and presumably they reached Los Angeles 

 about two days later. 



Altogether Cooper spent more than five months at Fort 

 Mojave; on the basis of the work at this point he described 

 two new species of birds and one land tortoise, and listed five 

 mammals, 16 birds, and three reptiles as new for California 

 (Cooper, 1861; Grinnell, 1902, p. 104). 



San Diego was evidently his next important collecting lo- 

 cality, though at this period he apparently spent a short time 

 only at this point. 



Late in 1860 the Geological Survey of California was or- 

 ganized by J. D. Whitney, The Department of Zoology of 

 the Survey was instituted and Dr. Cooper appointed to the 

 place of Zoologist (Whitney, 1865, p. xi) on July 1, 1861. 

 Shortly after his appointment he traveled by land from San 

 Diego to San Francisco. He remained in the city until 

 August 9, on which date he made a trip to Monterey by 

 water, where he was occupied in making collections from 

 August 12 to September 26 (Cooper 1870b, p. 45; 1871b, 

 pp. 756-757). About this time he must have worked in the 



