< Al'ODA. TIIALASSINAD^E. 



MACROURA. 



(1ENUS GEBIA. LEACH. 



CANCER (Astacus). Penn. 



GEBIA. Leach. 



Generic Character. Antenna; inserted in nearly the same ho- 

 rizontal line : external very slender, without any vestige of a 

 moveable scale at the base ; the seta very long, its joints sub- 

 elongate : internal very short, the double seise rather longer than 

 the peduncle, which is dilated on the outer side at the base. Ex- 

 ternal pedipalps pediform, slender. First pair of feet somewhat 

 robust, nearly equal, straight, the arm becoming trigonous for- 

 wards ; the wrist short, rounded ; the hand elongate, imperfectly 

 cheliform ; the moveable finger large, turning down to the im- 

 moveable one, which is not half its length. The remaining pairs 

 of feet slender, slightly compressed, monodactyle. Carapace 

 narrowed anteriorly, terminating in a short triangular rostrum. 

 Abdomen narrowed at each extremity, somewhat depressed. 



THE two recorded British species of this genus so nearly 

 resemble each other, that there is perhaps still some doubt 

 whether they exhibit more than sexual distinctions. 



