EXPLANATION OF THE PLATES. 



Xlll 



FIG. 3. Cellaria cirrata 



4. a. Fungia patellaris, under side. 

 b. Ditto, upper side. 



PLATE III. RADIARIES. . 



FIG. 1 . Cephea mosaica ................. . 



a. a. Arms of ditto. 



2. Echinus esculentus, portion of the shell 



shown externally. 



a. a. a. Groves. 



b. b. Alleys. 



c. c. The lateral groves. 



d. The intermediate one. 



3. Inside of the same shell. 



a. a. The dentated suture. 



b. The middle ridge marked out on each 

 side into transverse pieces. 



c. c. The alleys, with pores for the suckers. 



d. One of the frames to which the jaws 

 are fixed. 



4. Spines of Echinus cidaris. 



a. Muscular fibres inserted in the base of 

 the spine, and surrounding the ball and 

 socket joint. 



b. The muscular capsule laid open, and the 

 muscles attached to the base of the spine 

 turned back. 



c. The origins of the muscles surrounding 

 the ball or tubercle. 



d. One of the tubercles. 



5. One of the suckers of E. esculentus, 



a. The sucker ; the pore in the centre is 

 supposed to be a spiracle connected 

 with the respiration of the animal. 



b. The stalk of the sucker. 



6. The suture of a portion of the alleys at the 



lateral grove, in which the transverse 

 pieces are convex. 



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