HARD PARTS OF THE COMMON CRAB. 181 



each consists of a dense, solid body (6) , and a movable, 

 two-jointed portion (/?). The body is the basal joint or 

 basipodite, which is greatly thickened and elongated, and 

 which carries a stout, cutting blade upon its inner end. 

 The two-jointed portion (p) is the mandibular palp. It 

 bears a general resemblance to the endopodite of an ordi- 

 nary appendage, but its mode of development, which will 

 be noticed later, has induced most authorities to regard it 

 as without an homologue in a typical appendage, and ac- 

 cording to this view the mandibular endopodite is absent, 

 as well as the exopodite. Near the ends of the mandible 

 notice two plates, or apodemata, which run inwards, and 

 furnish attachment for the mandibular muscles. 



g. The remaining appendages are arranged in a longi- 

 tudinal row along the anterior margin of the carapace ; 

 the antennules in the centre, the eyes on the outside, and 

 the antennae between the eyes and the antennules. 



1. The antenna (Fig. 98) consists of an enlarged, ir- 

 regular basal joint (a), which is so firmly fastened to the 

 shell that it admits of hardly any motion, and which 

 carries a hairy spine (b) ; and a slender terminal portion, 

 or flagellum (c) , which consists of two long basal joints, 

 and a great number of short rings. 



FIG. 98. Outer surface of left antenna of Callinectes 

 hastatus; natural size. (Drawn from nature by W. K. 

 Brooks. ) 



a. Basal joint, b. Spine, c. Flagellum. 



FIG. 99. Outer surface of left antennule of 

 Callineetes hastatus; natural size. (Drawn from na- 

 ture by W. K. Brooks. ) < 



a. Basal joint, b. Shaft, c. Flagella. FIG. 99. 



Carefully disarticulate the antennae, and place them 

 with the other appendages. 



