464 BULLETIN OF THE BUREAU OF FISHERIES. 



(39) THE CHONDRIA ASSOCIATIONS. 



Chondria tenuissima is abundant on rocks and larger algae below low-water mark 

 along somewhat sheltered shores ; it was dredged as deep as 2 to 5 fathoms at Phalarope 

 station 7;^, but the species is on the whole rather characteristic of the upper level of the 

 sublittoral region. Chondria tenuissima var. Baileyana is less common, but found 

 in similar situations. 



Chondria dasyphylla is also found on rocks and larger algse and sometimes on Zostera 

 below low-water mark. It is a coarse species, generally present in less sheltered situ- 

 ations than Chondria tenuissima and was dredged in 4 to 10 fathoms, chiefly in the 

 easterly portion of Vineyard Sound. Chondria scdijolia is closely related to C. dasy- 

 phylla, and has been classed as a variety of the latter; it is less common, but is found 

 in similar situations. 



All the species of Chondria are members of the warm-water sublittoral formation 

 (b), preferring shallow water and sheltered situations. 



(40) THE DASYA ASSOCIATION. 



Dasya elegans is very abundant during the late summer below low-water mark, 

 generally in sheltered situations on Zostera, on larger algse, and occasionally on stones; 

 it was dredged over sandy and stony bottoms in 2 to 13 fathoms and has a wide and 

 scattered distribution throughout the Bay and Sound. The species is a member of the 

 warm-water sublittoral formation (b) and is also frequently conspicuous in the Zostera 

 formation (c). 



(41) THE POLYSIPHONIA ASSOCIATIONS. 



Of the 12 species of Polysiphonia found in this region 8 are sufficiently common to 

 present conspicuous associations. 



Polysiphonia elongata, the largest species, grows on stones and rocks in fairly deep 

 water over sandy, shelly, and stony bottoms in 2 to 17 fathoms (most plentiful in 5 to 13 

 fathoms). The species is common and widely distributed throughout Vineyard Sound, 

 but is found only in the lower portion of the Bay (chart 246). It is present in both the 

 warm- and cool-water sublittoral formations, but is more plentiful in the latter. 



Polysiphonia fibrillosa is common at Woods Hole in the summer, frequently forming 

 a zone on rocks at and just below low-water mark. Although characteristic of the 

 upper region of the warm-water sublittoral, the species was dredged at several scattered 

 Stations in Vineyard Sound in 2 to 1 1 fathoms. 



Polysiphonia Harveyi and P. Olneyi form tufted growths on eel grass in quiet water, 

 and are members of the Zostera formation (c). 



Polysiphonia nigrescens is very abundant on stones and shells frequently over 

 muddy bottoms in i to 15 fathoms (most plentiful in 5 to 10 fathoms). The species is 

 widely distributed in both Bay and Sound (chart 247), and is present in both the cool- 

 and warm-water sublittoral formations. 



Polysiphonia urceolata is abundant in the spring and very conspicuous in the zone 

 of red algse on stones and wharves below low-water mark. The species at that season 

 is probably widely distibuted in both the Bay and Sound and is then a prominent mem- 



