NATURAL HISTORY. 473 



Class VII. . CRUSTACEA. (Lat. Crusta, a crust or shell.) 

 Sub-class I. . MALACOSTRACA. ( Gr. MaAa/cof , soft ; uarpaKov, & 

 shell.)* 



Order I DEC APOD A. (G?. At'/ca, ten ; irov?, a foot.) 



Sub-order I. DECAPOD A-BRACHYUKA. (Gr. Bpa^vf, short ; ovpd, a tail.) 

 Family I. . . Canceridse. (Lat. Cancer, a Crab.) 



Pagurus, the Crab. 



The CRUSTACEA are almost all aquatic animals. They have 

 no internal skeleton, but their body is covered with a strong 

 crust, which serves for protection as well as for strength. 

 Their whole framework consists of a series of rings fitted to, 

 and working in each other ; some forming limbs, and others 

 developing into the frame work supporting the different organs. 

 From this reason, they and the remaining animals, as far as 

 the star-fishes, who have no limbs, are called " articulated" 

 animals. 



* So called because their shell is soft compared with that of the univalve or bivalve 

 molluscs. 



