Handbook of Paleontology 163 



flats, just as sandy or rocky beaches, may be, and have 

 been, divided into a number of zones each with its 

 characteristic life. Near the top of a mud beach there 

 may be rocks and boulders. Seaweeds are practically 

 lacking though there may be a few stunted specimens. 

 The Acorn Barnacle and Periwinkles (Littorina lit- 

 torea) may be abundant on the rocks, and crabs, such- 

 as the Green Crab, may be found among the stones. 

 Below the bouldery zone one may find a sandy mud 

 with clams such as Mya arenaria, both young and old, 

 in abundance. The Acorn Barnacle, Edible Mussel 

 and Periwinkle also live on the stones here. Worms, 

 such as the Clam Worm, are found under the stones 

 and certain crabs are common everywhere. This area 

 will gradually grade into the typical muddy areas. 

 Then there are zones where the eel-grass is scattered 

 and other zones where there is a thick growth of eel- 

 grass ; there are many animals that live on and among 

 the eel-grass ; several species of snails, some of them 

 very delicate species; worms (Spirorbis) ; compound 

 ascidians in jelly like masses; hydroids ; clusters of 

 shelly or horny bryozoans ; small crustaceans (for ex- 

 ample, isopods) ; flat-worms etc. Scallops (Pecten) 

 are found at the base of the plants and the Common 

 Prawn has its true home here and occurs in large num- 

 bers, swimming about freely. Also to be looked for 

 are the Edible Crab, Mud Crab, Hermit Crab, Com- 

 mon Shrimp and Green Shrimp. The Common Shrimp 

 is less abundant where the eel-grass is on sandy bot- 

 toms. The Green Shrimp is often abundantly asso- 

 ciated with the Common Prawn. 



Just as with the other associations a survey will be 

 given of the fauna to be searched for where the bot- 



