430 REPORT dF^K)MMISSIONER OF FISH AND FISHERIES. 



Polyps. 



Page. 

 Paractis rapiformis , 363 



PROTOZOA. 



Siionges. 



Page. 

 Clioua sulpliurea 427 



Page. 

 Massive siliceous sponge 427 



Foraminifera. 



Page. 

 Several species 421 



II. 8. — FAUNA OF THE MUDDY BOTTOMS OF THE BAYS AND SOUNDS. 



The muddy bottoms are inhabited by a considerable number of 

 species, which find their true homes in such localities. Most of these 

 are either burrowing or tube-dwelling kinds. A few creep or swim 

 abont over the surface or conceal themselves in the superhcial layer of 

 mud aud vegetable debris. 



The character of the mud itself is quite various, aud the different 

 kinds are often inhabited by different groups of animals. The mud may 

 be very thick, heavy, and tenacious, consisting chiefly of clay ; such 

 mud is usually inhabited by few species of animals. It may consist of 

 finely comminuted sand, mixed with more or less clay; such bottoms are 

 more favorable to animal life. In other places it consists partly of one 

 of the preceding kinds intimately mixed with large quantities of decay- 

 ing vegetable debris, derived chiefl}^ from eel-grass and algne; such mud, 

 unless too fetid, is often full of animal life. In some cases, especially 

 in well-sheltered localities, where the water is tolerably pure, the mud 

 may contain large quantities of living and dead microscopic organisms, 

 both animal and vegetable, and these may even constitute more than 

 one-half of the bulk of the mud, which, in such cases, is peculiarly soft 

 aud floccnlent; such mud is extremely favorable to many kinds of ani- 

 mals that feed on the microscopic organisms, especially the bivalve 

 shells, Holothurians, and many Annelids, and the " menhaden " among 

 fishes. The last variety of bottom, when it has a substratum of sand 

 or gravel a few inches below the surface, is the most favorable kind for 

 oysters, which grow very rapidly and become very fat in such places. 



In Vineyard Sound and ISTantucket Sound muddy bottoms are not 

 common, and are mostly of small extent, situated in coves, harbors, or 

 in places where the tides form eddies around projecting points of laud, 

 or in the lee of shoals. 



lu Buzzard's Bay the bottom is muddy over the greater part of its 

 area, except a region of sandy aud shelly bottom in the central part. 



In Long Island Sound the bottom is generally muddy throughout its 



