56 University of California PublicatioDS in Zoology [Vol.12 



21.. Eight miles east of Picacho. California side; camp in river 

 bottom at lower end of "Charlie's Valley," which in turn is just 

 below Canebrake Canon. Because of the eastward swing of the river 

 in the vicinity of Picacho, eight miles east of Picacho is also eight miles 

 brlow Picacho. April 17 to 21. 



22. Five miles above (or north of) Laguna, Arizona side; camp in 

 river bottom near base of first hills above silted-in area ; April 21 to 26. 



23. Four miles above (or north of ) Po^/ioZes, California side ; visited 

 April 23, from our camp on the opposite side of the river. 



24. Potholes, California side; camp in river bottom ,jast below the 

 head-gate ; April 26 to 29. 



25. Four miles below Potholes, California side ; camp in river bot- 

 tom ; Grinnell and Dixon ; April 29 to ]May 2. 



26. Five miles northeast of Yuma, California side ; camp in river 

 bottom; Stephens and Jones; April 30 to May 3. 



27. Five miles above (northeast of) Yw ma, California side; camp in 

 river bottom ; Grinnell and Dixon ; May 2 to 5. This station was but 

 a half-mile or so from the preceding. 



28. Yuma, Arizona side ; camp about half a mile up the Gila River 

 from its mouth, on the shore towards Yuma and within two miles east 

 of that town ; Stephens and Jones ; May 3 to 7. 



29. Near Pilot Knob, California side; camp on river bank at site 

 of the old Hanlon Ranch, marked by a group of date palms. This is 

 also the site of the "American Girl Pump," of the Yuma quadrangle, 

 U. S. G. S. ; but only rusting machinery and pipes, and a pile of ashes, 

 marked the place at the time of our visit. Grinnell and Dixon ; May 

 5 to 15; Stephens and Jones, May 7 to 15. The season's field-work 

 was concluded on May 15. 



As will have been noted, our collecting stations were usually estab- 

 lished on alternate sides of the river successively. It proved impos- 

 sible to propel the heavy scow directly across because of the strong 

 current. In two places, however, a limited amount of collecting was 

 done on exactly opposite sides of the river, this being accomplished 

 through the use of the skiff alone. 



From each of the base camps as a center, hunting and trapping 

 were carried on as far radially as proved practicable. It was. our 

 effort to test every sort of ground available, that is, each association 

 represented. Three of the four members in the party were constantly 

 engaged in trapping for mammals. Trap lines were run in different 

 directions, iisually from the river's edge back to the highest parts of 



