THE SHORE CRAB. 73 
openings by which water is taken into the branchie ; 
the efferent canals from the branchiz terminate on 
each side of the palate. The abdomen is short, and 
inflexed beneath the body; in the male it is com- 
paratively narrow, but in the female it is very broad, 
and acts as an ovarian pouch. It has from five to 
seven joints. Between the legs, and extending up to 
the mouth, is the sternwm, divided into five seg- 
ments. In the female the genital openings will be 
found on the third segment of the sternum ; there 
are two, one on each side, not very distant from the 
middle line. In the male the genital openings are 
either on the last sternal segment, or at the bases of 
the last pair of legs. Appendages. There are four 
pairs of ambulatory legs, each divided into five 
joints. The basal joint is the cova; that next it the 
trochanter, which is followed by the femur, the 
longest joint of the leg ; then comes the tibia, divided 
into two portions by an oblique suture: the last joint 
is the tarsus. The anterior pair of legs are larger 
and chelate, with a movable finger. The trochanter 
is generally called the arm; the femur the wrist ; and 
the tibia the hand, while the movable finger repre- 
sents the tarsus. On each side of the mouth there 
are six pairs of modified appendages. The three 
outer pairs are called maxillipedes; the two next 
pairs, which are delicate, the maxille; and the 
anterior pair, which is strong and toothed, the man- 
dibles. The examination of these organs is better | 
deferred until the internal structure has been studied. 
In front of the mouth will be seen two pairs of 
antennce. The “internal antenne,’ or antennules, 
are the smaller, and lie under the front. The exter- 
