160 LIFE BY THE SEASHORE. 



the shield by a distinct movable suture The inturning of 

 the carapace in the frontal region has, as it were, carried in 

 with it the insertion of the antennules, so that we no longer 

 find these on the dorsal surface, but placed in little pits 

 beneath the margin of the shield. They are very short, 

 consist of one filament only, and are carried doubled up 

 when not in use. The eyes, instead of lying above the 

 antennules, are shifted outwards, and lie in somewhat elon- 

 gated sockets, or orbits, into which they can be completely 

 retracted. The very short antennae, without trace of scale, 

 are squeezed in between orbits and antennules. Their 

 peduncles are very short, the basal joints being lost in a 

 triangular plate which lies in front of the mouth. 



FIG. 50. Maxillipedes, or foot-jaws, of edible crab (A) and lobster (B). In 

 each figure, g is the gill, s the gill separator, ex the outer branch, en the 

 inner branch. 



On the minor peculiarities of the mouth parts we need not 

 dwell. It is sufficient to note that they are more crowded 

 and overlap one another more completely than the similar 

 parts in the lobster. The point which is especially worth 

 notice, however, is the character of the third maxillipede-s. 

 As is seen in the figure, in the lobster these are distinctly 

 leg-like, but differ from the walking legs proper in that they 

 have a slender outer branch in addition to and arising from 

 the same base as the leg-like inner branch. The third 

 maxillipede of the crab has in essence the same structure, 



