96 University of California Publications in Zoology [ Vou. 14 
represented by a single sector, comparable with the others into which 
the circle is divided. It has seemed a fairer procedure to represent 
the calcium carbonate as a smaller circle at the center of the large 
one and eneroaching upon the area of all the sectors.2° The area (not 
the diameter) of this inner circle is proportionate to the percentage 
of calcium carbonate in the sample. Quantities less than two per cent 
have not been represented in these symbols. 
With the calcium carbonate there has been included, as already 
stated the shells and shell fragments which were dried and weighed 
without any chemical treatment. 
In interpreting these symbols, it must be borne in mind that the 
coarser grades of stippling do not invariably represent pure gravel, 
but that shells and shell fragments are thus likewise designated. The 
size of the circle representing calcium carbonate will commonly serve 
as a clue to the nature of these coarser particles, however, and in any 
doubtful case their character can be determined by reference to the 
table. 
In plate 6 have been presented the results of the analyses of the 
tube specimens obtained by the use of the ‘‘Albatross’’ bottom- 
sampling apparatus (except at four stations, 5129 A, B, C, and D, 
where the Ekman apparatus was used). The stations are arranged 
along the (interrupted) horizontal axis from the northern end of 
the bay, the distances being proportional to the actual distances be- 
tween the stations, independently of direction. The vertical axis 
represents depth in centimeters. In plotting these circles the same 
system has been followed as that employed in the construction of the 
previous chart. 
Plate 7 represents the proportions of nitrogen at various levels in 
these tube samples. The areas of the circles are proportional to the 
percentages of nitrogen. The absolute figures will be found in Ap- 
pendix IV. They include all the nitrogen, however, combined.*" The 
method employed was that of Gunning. 
No extended discussion of these various conditions will be at- 
tempted here, partly because a more complete report upon these bottom 
deposits will probably be prepared within the coming year by one 
of the present authors, partly because we can at present discern few 
26 Of course it would not be likely to encroach equally upon all of these, 
but such details can hardly be taken into account in constructing a diagram 
such as this. 
27 Dr. Alsberg writes: ‘‘A few of the muds were tested for nitrates, and 
none were found. The nitrogen evidently occurs in organic compounds, the 
composition of which may vary widely. All the nitrogen was determined.’’ 
