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 shefl 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, Area 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 jornicata 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. In a 

 few cases the deposits represented upon the chart by the conventional shading for mud 

 are fairly pure clay. 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 nferely 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 



