BRANCH ARTHROPODA: CRUSTACEANS 153 



when disturbed. They move as readily backward or 

 sidewise, "crab-fashion," as forward. They are of 

 various colors and markings, often so patterned as to 



FIG. 37. Some crabs and barnacles of the Pacific coast; the short sessile 

 acorn barnacles in the upper left-hand corner belong to the genus Bal- 

 anus; the stalked barnacles in the upper right-hand corner are of the 

 species Pollidpes polymenus; the largest crab (upper left-hand) is 

 Brachynotus nudus; the one in left-hand lower corner is a young rock- 

 crab, Cancer prodiictus; the crab in the sea-weed at the right is a kelp- 

 crab, Epialtus prodnctus, while the two in snail-shells in lower corner 

 are hermit-crabs, Pagnms samuelis. (From living specimens in a tide- 

 pool on the Bay of Monterey. California.) 



harmonize very perfectly with the general ^cplor and ap- 

 pearance of the rocks and sea-weeds among which they 



