138 



ZOOLOGY 



Shrimps and prawns ' belong to a thin-skinned, long-tailed 

 family of Crustacea.^' They are extremely common in bays 

 along our coast, and even penetrate into rivers. Two river 

 shrimps ^ are found in the United States east of the Mississippi 

 River. The.se Cru.stacea are able to maintain their enormous 

 numbers only bj- virtue of their great rejoroductive capacit}-, 

 which is the more necessary since they furnish almost the 

 entire food .supply for many kinds of fishes and other foes. 



Fig. 132. — Palaemonetes vulgaris, a common shrimp. 



Even in the principal shrimping grounds of the United States 

 — such as San Francisco and New Orleans — there is said to 

 be no diminution in the numljers of slu'imps. 



Tlie burrowing shrimps (ThalassinicUe *) are crayfish-like 

 species that liurrow in the mud flats of our coast. They 

 remain concealed during the day. They are much smaller 

 than craj'fishes and are difficult to oljtain, so the}- have no 

 market value and are commonly little known. 



The hermit-crabs (Pagurifla?'' ) occupy a position inter- 

 mediate between the long and short tailetl decapods in respect 



'The term "shrimp" is applied to the smaller species, and " prawns " to 

 the larger. 

 2 Fig. 1.32. 



^ Palcemon Oh touts and Palcomonclcs exilipes. 

 ■* thakissinos , color of the sea. 

 ^ pagouros, a kind of crab. 



