In June, I920, Dr. G. F. McEwen, while on a voyage from San Diego to Seattle and back, made a number of surface hauls of from two to five gallons of water from the decks of the passenger steamers. In connection with this work and with that of collecting water samples he secured the attention and interest of Mr. J. R. Mortensen, Second Officer of the steamer Queen of The Admiral Line, who volunteered to take similar collections for the use of the Scripps Institution at such times as he might be able to find. In the six months from July to December, inclusive, he was able to make a total of sixty-six collections of phytoplankton fairly well distributed as to both time and locality. The collections taken by Dr. McEwen totaled one hundred and one, and were taken at hour or half-hour intervals when it was found convenient in the two or three days actually spent at sea. In both series catches were made by the simple process of throwing a canvas bucket into the water, hauling it up and pouring the water thus secured through a filtration net of number 25 bolting silk. Most of the samples of water from which the catches were taken were small (two or three gallons), hence the catch was made with so few casts of the bucket that the ship had not made much progress during the hauling. For this reason sampling was fairly indicative of surface distribution of organisms in the immediate vicinity of the catch. Enumeration was done by a modified Sedgwick-Rafter method. Estimates were recorded in number of specimens per liter. The records were then tabulated according to areas based on prominent localities, each area being about sixty to one hundred miles in length parallel to the coast line. Fourteen such areas were designated as indicated on the accompanying map. Each of these fourteen areas showed at least a few diatoms in all or nearly all of the catches made by Mr. Mortensen, but in the more frequent catches made by Dr. McEwen on the single round trip there were eleven barren catches taken in the areas between Point Cabrillo and Cape Disappointment. On the other hand, some of the fifty productive catches in this area were very large. Thirteen species of diatoms were recorded for the Mortensen series and thirty-three species for the McEwen series, the two lists being identical as far as the former goes. A few of the names are merely catch-all designations for unrecognized species or those represented by very small numbers. Most