CRUSTACEA. 117 



beach or on the bottom. The habits of this genus 

 are highly entertaining.* 



Identification. — The development of the mouth 

 and its organs ; the number of the eyes, and 

 whether they are immoveable or borne on a foot- 

 stalk; the character of the foot-jaws, feet, and 

 false-feet ; the presence or absence of a carapace ; 

 the manner in which, and the organs by which, 

 breathing is performed; the development of the 

 abdomen ; the form and office of the plates near its 

 extremity; the form of the antennse with their 

 appendages ; the presence and the form of the 

 frontal beak ; — are the points that principally claim 

 attention in distinguishing the various genera. 



Authorities. — I am mainly indebted to the valu- 

 able "Hist. Nat. des Crustaces" of Professor M.- 

 Edwards for the general arrangement of the Class, 

 slightly modifying his nomenclature. For the 

 British species Professor Bell's " Stalk-eyed Crus- 

 tacea " has been the text-book, so far as one Order 

 extends ; while for another the " British Entomo- 

 straca" of Dr. Baird has afforded materials. For 

 the rest I have consulted the magnificent collection 

 in the British Museum, and the " List of Speci- 

 mens ' in that collection by Mr. Adam White, 

 adding a few new species recently introduced to our 

 British Marine Fauna by myself and others. 



Crustacea. 



Articulated animals ; provided with jointed 

 limbs ; breathing by gills, sometimes covered, 

 sometimes exposed, but not inclosed in special 

 cavities of the body: eyes generally two, com- 



* See "Aquarium," p. 163, et seq. 



