94 University of California Publications in Zoology [ Vou. 14 
The limited quantities of vegetable remains found in certain of 
the bottom samples have likewise been indicated in another column. 
These materials were sometimes more prominent than their slight 
(dry) weight would seem to indicate. At the upper end of the bay, 
in particular, drifted wood fragments were abundant in certain 
dredge-hauls. These were completely waterlogged and much eroded, 
sometimes forming veritable wooden pebbles. Other remains of land 
plants, perhaps also of fresh-water ones and of Zostera, occurred 
freely throughout the bay, though forming a scarcely appreciable 
fraction of the dry weight of most of the bottom samples. Marine 
algae seem to have contributed almost nothing to these deposits. 
In our table, material which passed through the two-millimeter 
sieve has been divided into 
< 9? 
‘sand’’ and ‘‘mud’’. The words are 
evidently used in a more restricted sense here than in our field notes. 
““sand,’’ in which 
these finer particles predominated, but which were none the less 
mixtures of materials of various grades of coarseness, and which com- 
In the latter, bottom deposits were designated as 
monly contained more or less mud as well. Likewise practically all 
of the ‘‘muds’’ contained a certain proportion of coarser ingredients. 
The method which we adopted for separating the mud and sand and 
the distinction which was drawn between the two have already been 
discussed (p. 92). Where the occurrence of mud is not expressly 
indicated in our table, it may be assumed that the material passing 
through our finest sieve was entirely composed of sand, or at least 
of non-muddy matter. Finely divided shell fragments sometimes 
constituted an appreciable fraction of this material. 
In certain eases, notably at the dredging stations 5738, 5778, 5808 
and 5809, the bottom samples which were preserved for study com- 
prised only the finer ingredients, the stones which here abounded being 
too large to be included. Thus the figures given in our table do not 
fairly express the actual character of these bottoms. Indeed no really 
quantitative treatment of such deposits would be possible without 
making an inventory of the entire dredge-haul. This is particularly 
true of the deeper portions of the Golden Gate, where hundreds of 
pounds of large stones, with very little finer materials, were some- 
times brought up at one time. Lists of the larger stones, with their 
dimensions and weight, were prepared for two such stations, D—5845 
and 5846, and some of these data have been included in the records 
for those stations, but no account was here taken of the finer materials. 
The bottom conditions in San Francisco Bay, so far as revealed 
