15. de Laubenfels, M. W. Sponges collected on the Presidential 



cruise of 1938. 7 pp., 1 fig., June 21, 1939. (Publ. 3540.) 



16. McIntosh, Allen. A new dicrocoeliid trematode collected on 



the Presidential cruise of 1938. 2 pp., 1 fig., June 8, 1939. 

 (Publ. 3541.) 



17. Hyman, Libbie H. Polyclad worms collected on the Presidential 



cruise of 1938. 13 pp., 15 figs., June 17, 1939. (Publ. 3542.) 



18. Steward, Julian H. Notes on Hillers' photographs of the 



Paiute and Ute Indians taken on the Powell expedition of 

 1873. 23 pp., 31 pis., July 21, 1939. (Publ. 3543.) 

 79. Johnston, Earl S., and Weintraub, Robert L. The determi- 

 nation of small amounts of chlorophyll — apparatus and method. 

 5 pp., 2 pis., 2 figs., July 31, 1939. (Publ. 3545.) 



20. Perry, Stuart H. The Helt Township (Indiana) meteorite. 



7 pp., 9 pis., Aug. 28, 1939. (Publ. 3546.) 



21. Abbot, C. G., and McCandlish, N. M. The weekly period in 



Washington precipitation. (Roebling Fund.) 4 pp., July 27, 



1939. (Publ. 3547.) 



22. Wetmore, Alexander. Birds from Clipperton Island collected 



on the Presidential cruise of 1938. 6 pp., Aug. 11, 1939. 

 (Publ. 3548.) 



23. Meier, Florence E. Stimulative effect of short wave lengths 



of the ultraviolet on the alga Stichococcus bacillaris. 19 pp., 

 4 pis., 1 fig., Sept. 26, 1939. (Publ. 3549.) 



24. Resser, Charles Elmer. The Ptarmigania strata of the 



northern Wasatch Mountains. 72 pp., 14 pis., Oct. 26, 1939. 

 (Publ. 3550.) 



25. Schmitt, Waldo L., and Schultz, Leonard P. List of the 



fishes taken on the Presidential cruise of 1938. 10 pp., Jan. 4, 



1940. (Publ. 3551.) 



(vi) 



