INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 303 



5. Bocky bottoms below low-water mark. 



6. Stony, gravelly, and shelly bottoms. 



7. Sandy bottoms. 



8. Muddy bottoms. 



9. Free-swimming and surface animals. 

 10. Parasitic animals. 



It must, however, be constantly borne in mind that very few kinds 

 of animals are strictly confined to any one of these subdivisions, and 

 that the majority are found in two, three, or more of them, and often in 

 equal abundance in several, though each species generally prefers one 

 particular kind of locality. In other cases the habits vary at different 

 seasons of the year, or at different hours of the day and night, and 

 such species may be found in different situations according to the times 

 when they are sought. The more common and characteristic species 

 are, however, pretty constant in their habits and may be easily found 

 in their respective stations at almost any time. 



Since those animals that inhabit the shores, between tides, are most 

 frequently seen and can be most easily obtained and studied by those 

 who are not professional naturalists, I have entered into more details 

 concerning their habits and appearances than in the case of those 

 obtained only by dredging. Such species as have not been previously 

 named and described in other works will be more fully described in the 

 systematic list, to follow this report, aud references will there be given 

 to descriptions of the others. 



II. — 1. ANIMALS INHABITING- THE ROCKY SHORES OF THE BAYS AND 



SOUNDS. 



The principal localities where these animals were studied and col- 

 lected are at Nobska Point, just east of Wood's Hole ; Parker's Point, 

 between Great Harbor and Little Harbor, near Wood's Hole ; the neck 

 of land north of Wood's Hole Channel ; several localities on Kaushon 

 and the adjacent islands ; and numerous localities on the shores of Long 

 Island Sound, as at Savin Eock and Light-House Point, near New 

 Haven; Stony Creek; Thimble Islands, &c. 



In all these places the rocks, in a zone extending from near low- 

 water mark of ordinary tides to near half tide, are generally covered 

 with an abundance of " rock- weeds," (Fucus nodosus and F. vesiculosus,) 

 which hang in great olive-brown clusters from the sides of the rocks 

 or lie flat upon their surfaces when left by the tide, but are floated up 

 by means of their abundant air-vessels when the tide rises. Mingled 

 with these are several other algre, among which the green " sea-cabbage " 

 (Ulva latissima) is one of the most abundant. Below this zone of 

 Fucus there is a narrow zone which is only exposed during spring-tides; 

 in this the Ulva and many other more delicate green and red algae 

 flourish. Above the Fucus-zone there is another zone of considerable 

 width which is covered for a short time by every tide ; and still higher 



