HARD PARTS OF THE CRAYFISH OR LOBSTER. 185 



nules, and antennae. In this view, it is plain that the eyes 

 are the first, or most dorsal pair of appendages, the an- 

 tennules next, and the antennae third. This arrangement 

 is obscured, on the outer surface, by the great size of the 

 eyes, in accordance with which these appendages have 

 pushed the second and third pairs towards the middle line 

 of the body. 



XIX. THE HARD PARTS OF THE CRAYFISH OR 



LOBSTER.* 



I. THE body is divided into two well-marked regions, 

 the anterior, unsegmented portion, or cephalofhorax, to the 

 lower surface of which the walking limbs are attached ; 

 and the more narrow, posterior portion, or abdomen, 

 which is divided into seven movable portions or joints. 

 In a view of the dorsal surface, notice : 



a. The groat shield-like plate, or carapace, which covers 

 the back and sides of the cephalothorax. 



b. The groove, or cervical suture, which divides it into 

 an anterior and a posterior region. 



c. The long spine, or rostrum, situated upon the median 

 line of the anterior margin of the carapace. 



d. The stalked eyes, and long, many-jointed anten- 

 nules and antenna' , which project from below the anterior 

 margin of the carapace, on each side of the rostrum. 



e. The live pairs of long, jointed, walking limbs, which 

 project from below the sides of the carapace. 



/'. The dorsal surfaces, or terga, of the segments of the 

 abdomen. 



1. The first, second, third, fourth, fifth, and sixth of 



* This section is copied, with slight changes, from "Biology," by 

 Huxley and Martin. 



