HARD PARTS OF THE COMMON CRAB. 169 



it may be preserved in alcohol, or studied while fresh. If 

 specimens are to be preserved for winter work, they 

 should be bled before they are placed in alcohol. This is 

 done by puncturing the soft integument of the dorsal sur- 

 face between the posterior edge of the carapace and the 

 first abdominal somite. They should then be placed in 

 eighty or eighty-five per cent alcohol, which should be 

 renewed in four or five days. Specimens for studying 

 the hard parts may be dried in the sun. 



I. The Dorsal Surface. 



The dorsal surface of the body is almost entirely cov- 

 ered by the carapace, which, in Callinectes, is about three 

 times as wide as it is long ; irregularly rhomboidal, with 

 its outer angles prolonged into two sharp-pointed, pro- 

 jecting horns. Observe : 



a. The anterior, nearly semicircular, serrated margin. 



1. The middle of this margin is marked by a concave 

 notch, beneath which a short spine projects from the 

 middle line of the body. The spine does not form part 

 of the carapace, but is attached to the ventral or sternal 

 portion of the antennary somite. 



2. On each side of the spine notice that the antennules 

 project beyond the overhanging edge of the carapace. 



3. Outside these, on the edge of the carapace, the me- 

 dian pair of serrations. ( This pair of serrations, together 

 with the notch between them, represent the protruding 

 rostrum of the lobster or the crayfish. 



4. The next pair of serrations are rounded, and over- 

 hang the antennae, and outside them, on each side, is an 

 area, free from teeth, below which is the eye. 



5. The edge of the carapace, between this space and the 

 outer angle, is occupied by eight serrations, which are 

 nearly alike in size and shape. 



