Branch Arthropoda 6i 



II. — Study the carapace. Is its front margin denticulate .'' 

 Are there any sutures .'' Distinguish these parts, which 

 are marked off by the sutures : — 



a. The gastric lobe, a large, elevated, subtriangular 

 area in the middle of the front half. 



b. The cardiac lobe, a somewhat similar area, back of 

 the gastric lobe. 



c. The hepatic lobes, one on each side of these median 



lobes. 

 III. — Study the ventral surface; make a drawing of it. 

 See the large plastron which forms the under side of 

 the body. Notice the plates of which it is composed. 

 Notice the broad groove in which the abdomen rests. 

 In male specimens the abdomen is narrow ; in female 

 it is broad and rounded, its concave ventral surface 

 forming a chamber in which the eggs may be carried. 

 How many segments in the abdomen .' 



IV. — Study the six pairs of appendages attached to the 

 sides of the plastron. Beginning posteriorly, find four 

 pairs of walking legs, one pair of large chelae, and one 

 pair — the third — of maxillipeds. Are the appendages 

 similar in general structure to those of the lobster? 

 Study the appendages of the head. 



V. — Immediately in front of the third pair of maxillipeds 



are the second and first pairs of maxiUipeds. In front 

 of the latter are the large mandibles. Find the eyes. 

 How are they situated ? Find the antennules and the 

 antennae. 



VI. — Find a large orifice on each side of the head, opening 

 into the branchial chamber. Notice a membranous 

 flap on each side. See if this is a part of the second 

 maxilliped. 



VII. — Should you say that the crab is to be placed higher 



