482 



BULLETIN OF THE BTJREAU OF FISHERIES. 



Phyllophora Brodiaei, 7656, many; 7663, 7672 and 



7673, few. 

 Phyllophora membranifolia, 7659 and 7662, many; 



7657, 7660, 7663 (1907), 7664, 7666, 7672 (1907), 



and 7675, few. 

 Pleonosporium Borreri, 7675, few. 

 Polyides rotundus, 7659, many; 7660 and 7666' 



few. 

 Polysiphonia elongata, 7656, 7662 (1907), 7665, and 



7675, few. 



Polysiphonia nigrescens, 7659, many; 7656, 7664, 



7666, 7668, and 7672, few. 

 Polysiphonia urceolata, 7670, 7673, and 7675, few. 

 Polysiphonia violacea, 7664, few. 

 Rhodomela subfusca, 7656 and 7667, few. 

 Rhodymenia palmata, 7664, 7665, 7666, 7667, 7670, 



and 7671, few. 

 Seirospora Griffithsiana, 7660, few. 

 SpjTidia filamentosa, 7671, many; 7656 and 7675, 



few. 



Summarizing this statement of the algal vegetation in Buzzards Bay, it may be said 

 that the life conditions are much more favorable in the lower portions of the Bay than in 

 the upper, since the bottom is generally stony and the water clearer, because silt and 

 mud are less frequent. These characteristics are graphically shown on chart 227, and 

 it will be noted that the greater part of Buzzards Bay has a muddy bottom. Such 

 regions in the deeper waters are almost deserts as regards vegetation. The algal flora 

 of the upper portion of Buzzards Bay is, in the summer, composed of species character- 

 istic of the warm-water sublittoral formation, which also extends somewhat into the 

 lower portions of the Bay. However, the vegetation changes markedly toward the 

 entrance of the Bay, both as to its characteristics and its quantity, as is shown by 

 the above lists. Species appear which are peculiar to the cool-water sublittoral forma- 

 tion. Around the exposed reefs of Sow and Pigs the vegetation is typical of this forma- 

 tion, which is presented in even greater luxuriance off Gay Head. 



2. THE MIDDLE REGIONS OF VINEYARD SOUND. 



The conditions in Vineyard Sound differ from those of Buzzards Bay in several 

 respects. The tides which flow east with the flood and west with the ebb have a 

 velocity of i to 3 knots an hour, which is so strong a current that extensive deposits 

 of mud or fine silt are generally rendered impossible. The bottom is in consequence 

 chiefly hard sand, frequently mixed with shell fragments, gravel, or stones. There is 

 little or no mud in the middle regions of the Sound. The average depth is somewhat 

 greater than that of the Bay, but not enough to be an important factor in determining 

 the character of the vegetation. There are no large areas of shallows under 6 fathoms, 

 as are found in the upper portion of Buzzards Bay, the Middle Ground being the only 

 extensive region of shoal water, and that is composed chiefly of sand and is quite barren 

 of vegetation. 



Vineyard Sound within the limits of this Survey (that is, from a line drawn between 

 the westerly end of Cuttyhunk and Gay Head to a line between Falmouth Heights and 

 East Chop) has for convenience been divided into three regions as follows: (a) The 

 westerly portion from the entrance to a line between the west end of Naushon (Robinsons 

 Hole) and Kopeecon Point (Cape Higgon), (ft) the narrow portion of the Sound between 

 Naushon and Marthas Vineyard to a line connecting Nobska Point and West Chop, and 

 (c) the easterly portion of the Sound from the last line to one between Falmouth Heights 

 and East Chop. 



The westerly portion of Vineyard Sound includes large areas wth a bottom of hard 

 sand or sand with shell fragments, but exceptions to these conditions were found at a 



