32 BULLETIN OF THE BUREAU OF FISHERIES. 
Large beds of nearly pure sand are without doubt common in Vineyard Sound, 
and are occasionally met with even in Buzzards Bay. Such are the great shoals of 
shifting sand of which Middle Ground in Vineyard Sound is a fair sample. These are 
veritable submarine deserts, often being almost devoid of life. Despite Shaler’s asser- 
tion that in Vineyard Sound ‘‘the amount of sand at the disposition of the currents and 
waves is not large,” we believe that such transportation is sufficiently active in some 
localities to be a determining factor in distribution. In the vicinity of Middle Ground 
and Lucas Shoal we have frequently observed the water to be rendered turbid by sand 
and fine shell fragments which had been brought up by the currents from a depth of 
several fathoms. 
Beds of dead shells, accompanied by sand, gravel, or mud, occurred frequently, 
both in the Bay and in the Sound. These sometimes represented extinct mussel beds, 
though the shells of Spisula solidissima, Arca transversa, Venus mercenaria, Veneri- 
cardia borealis, Astarte castanea, Callocardia morrhuana, Anomia simplex, Pecten gibbus, 
and other lamellibranchs. sometimes occurred in great quantities. Among the gastro- 
pods, Crepidula fornicata is perhaps the only one which contributed materially to shell 
deposits, although the shells of many of the commoner species, occupied by hermit 
crabs, are frequently taken in great numbers. 
Under ‘‘mud’”’ is included a considerable diversity of material, differing in origin and 
in chemical composition, but agreeing in consistency and in general appearance. Ina 
few cases the deposits represented upon the chart by the conventional shading for mud 
are fairly pureclay. Beds of this last material occur, as is well known, at Gay Head and 
the neighboring parts of Marthas Vineyard, and outcroppings of it are met with along the 
shores at various points within the region. In the course of the dredging clay was brought 
up in Vineyard Sound near the island of Cuttyhunk. Most of the mud, however, is 
composed in considerable part of organic matter. It is dark in color, and frequently has 
an offensive smell. It may be either sticky or semifluid or it may contain enough sand to 
alter the texture visibly. According as the mud or sand seemed to predominate in such 
a mixture, it was listed as ‘“‘sandy mud”’ or ‘‘muddy sand.’”’ Sometimes such mixtures 
were called ‘“‘sand and mud;”’’ and in all probability the sand was at times overlooked, 
and the deposit was listed merely as ‘‘mud.”’ Indeed, it is likely that almost any sample 
of mud, however pure in appearance, would be found upon careful sifting or decanting 
to contain a certain percentage of sand, and sometimes small amounts of fine gravel or 
shell fragments. 
It had been our expectation to include in another chapter of this work the results of 
petrological and chemical analyses of the various bottom deposits, undertaken by Prof. 
Gilbert Van Ingen, of Princeton University. Thus far, however, Prof. Van Ingen has 
failed to complete his report upon these deposits, and its publication must therefore be 
deferred. The specimens upon which these analyses have been based were collected in 
1905 during the third series of dredgings by the Fish Hawk in Vineyard Sound and 
in the course of some supplementary dredging, during the following summer, in Buzzards 
Bay. Satisfactory bottom samples from the earlier dredgings had not been preserved. 
In the present instance they were obtained exclusively by the use of a canvas bag, which 
prevented the washing out of the finer constituents. The larger ingredients, such as 
stones and large shells, were not, however, included in these samples preserved, so that 
