Ecology of Animals 665 



Of these differing shore habitats, the rocky one has the greatest va- 

 riety of animal and plant life. Algae of many types are attached to 

 the rocks, and they in turn furnish attachments for sessile animals such 

 as hydroids and bryozoans. The upper part of the intertidal zone 

 often has masses of barnacles attached to the rocks, while further out 

 are many species of molluscs, tunicates, and sponges. Among the 

 loose stones near the high-tide mark are a great variety of crustaceans 

 and a few insects. Under other rocks are numerous worms, while 

 within the small pools left by the tide there may be sea anemones, bryo- 

 zoans, coelenterates, sponges, and many other animals. 



The sandy shore has but few algae as the shifting sands offer no 

 reliable attachment. There are, however, numerous burrowing crusta- 

 ceans, worms, and molluscs. 



The muddy shore also has an unstable substratum which furnishes 

 but little attachment for algae. Here as on the sandy shore, burrowing 

 animals predominate ; there are burrowing worms, clams, and crusta- 

 ceans. Starfish and sea anemones also may be found in this habitat. 



Fig. 216. — Oceanic zones extending from the shore to the depths. 



Sublittoral Zone. — Seaward from the eulittoral zone is the sub- 

 littoral. This extensive area varies in depth from about 50 meters to 

 some 200 meters. The bottom area is more uniform than that of the 

 eulittoral and is formed of sand, mud, and clay with the shells of mol- 

 luscs and some stones intermixed. Where the eulittoral blends into the 

 sublittoral there may be a large amount of the massive alga, Laminaria. 



