GENUS PORTUNUS. 63 



timate joint of the abdomen deeply emarginate at tip, for 

 the reception of the terminal, pentagonal, small one. 



Length one inch and a fifth, breadth one inch and two 

 fifths. 



The exuvia of this beautiful species is extremely com- 

 mon on the sea beach. It is known to the inhabitants by 

 the name of Sand Crab^ and is not used for food. It 

 seems to be closely allied to P. depurator and llvidus of 

 the European seas. The clypeus, strictly speaking, is 

 not three-toothed, those which appear to be lateral teeth 

 are in reality the anterior angles of the orbits of the eyes, 

 elevated. This species does not perfectly agree in all its 

 characters with the genus Portunus as defined by Doctor 

 Leach; this very acute naturalist says, that in this genus 

 there are two fissures in the hind margin of the orbits 

 of the eye, whereas in the species here described there is 

 but one; yet there is no doubt but the situation we have 

 here assigned to it is perfectly correct; the fissures inay 

 perhaps serve as good characters by which to separate the 

 genus into smaller divisions. 



(To be continued.) 



We are indebted to the friendship of Mr. C. A. Le- 

 Sueur for the plate of the Cecidomyia destructor (Hessian- 

 fly) with its parasite, which accompanies thepres nt num- 

 ber. 



I forgot to mention in its proper place that the parasitic 

 insect, Ceraphon destructor, which is so commonly mis* 

 taken for the Cecidomyia, after the business of propaga- 

 tion is performed, throws off its wings as a useless incum- 

 brance, in this respect resembling some species of the ge- 



