300 University of Califorma Publications in Zoology Vou. 13 
succeeded by Lieutenant-Commander H. B. Soule, U. S. N., during 
the years of 1912 and 1913. Much assistance has been received from 
Dr: Sumner and from Professor Kofoid, who upon Dr. Sumner’s 
resignation has had supervision of the work. A report by Sumner, 
Louderback, Schmitt, and Johnston (1914) has been published in 
which the physical conditions of the waters of San Francisco Bay are 
ably presented. The data for each dredging station in that paper 
have served as the basis for the discussion of the Mollusca that follows. 
A portion of the general results of the studies made upon the shell- 
bearing Mollusea dredged by the ‘‘ Albatross’’ in San Francisco Bay 
lends itself for a separate treatment preliminary to a general dis- 
cussion of the mollusecan fauna as a whole, and is herein presented. 
These results have to do with the so-called ‘‘quantitative’’ stations or 
“‘orange-peel bucket dredge hauls,’’ which comprise forty-three out 
of a much larger total number of dredgings. 
The orange-peel bucket dredge had not been previously used for 
biological exploration. Other devices of somewhat similar character 
have been employed by Petersen (1913, p. 3) whereby a definite 
amount of the bottom material could be obtained, thereby giving a 
quantitative measure of the number of organisms living within a 
definite area at a given locality. The orange-peel bucket dredge, de- 
seribed and figured by Sumner et al. (1914, p. 7), has proved very 
efficient. Regarding it, the authors state: ‘‘Its chief advantage lies 
in the taking of comparatively large masses of mud from a single spot, 
and particularly in the penetrating power of the apparatus which 
renders possible the capture of deeply burrowing annelids, lamelli- 
branches, ete.’’ Its capacity is given as 214 cubic feet. Since its 
diameter is 3.16 feet, it encloses a circular area containing 7.8 square 
feet. 
The material collected by means of this apparatus was carefully 
sorted and all of the macroscopic organisms preserved in formalin or 
in aleohol. At those stations where a considerable amount of material 
was obtained the following method of procedure was employed. All 
of the molluscan material from such hauls was first passed over a 
sieve of 5 millimeters mesh. The shells that remained in the sieve 
were identified, counted, measured, and the condition of the specimens 
was noted. The measurements consisted of the maximum, minimum, 
and modal lengths for each species in the haul. The fine material 
which passed through the sieve was thoroughly mixed and then quar- 
tered after the manner of taking ore samples. A convenient sample 
was then sorted and subjected to the same type of analysis as out- 
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