HARD PARTS OF THE COMMON CRAB. 



179 



c. Notice now on each side of the rectangular mouth 

 area, orperistome, a large orilice which communicates with 

 a capacious chamber under the carapace. 



This chamber is the branchial chamber, and the aperture 

 is that through which the water passes from the gills. 

 Lying in the mouth of this aperture, notice a thin, mem- 

 braneous, spoon-shaped scoop, the Scaphognathite, by the 

 movement of which, 

 during life, the water 

 is bailed out of the 

 branchial chamber. 



FIG. 94. Outer sur- 

 face of left first maxilli- 

 ped ; natural size. (Drawn 

 from nature by W. K. 

 Brooks. ) 



Letters as in Fig. 92. 



FIG. 94 



d. Raise up the edge of this scoop, and notice that it is 

 part of a thin, membraneous 

 appendage, the second maxilla 



en 



FIG. 95. Outer surface of second 

 maxilla; natural size. (Drawn from 

 nature by W. K. Brooks. ) 

 FIG. 95. sc. Scaphognathite. Other letters as 



in Fig. 92. 



Remove this appendage for examination, and notice that 

 the two divisions of the protopodite (b) and (ex) are 

 elongated, bilobed, and hairy. The lobes of the basipo- 

 dite (b) are long and slender, while those of the coxopo- 

 dite are more rounded. Outside these notice a short, 

 pointed, hairy process fen), which is the rudimentary 



