DECAPODA. PORTUNIDM. 



BRACHYUR4. 



GENUS OARCTNUS, Leach. 



CANCER, Auct. 



CARCINUS, Leach, Edwards. 



Generic Character. -- External antennae lodged in the inner 

 canthus of the orbit, the basal joint narrow and sub -cylindrical. 

 Internal antenna lying obliquely in nearly circular cells. Ex- 

 ternal pedipalps with the third joint excavated on the anterior 

 half of the inner margin., and dilated at the outer side. First pair 

 of feet somewhat unequal, the wrists with a strong spine on the 

 inner side, standing forwards ; the hands glabrous on the outer 

 surface ; second, third, and fourth pairs slightly compressed, with 

 the terminal joint long, styliform, somewhat four-sided ; the fifth 

 pair more compressed, formed for swimming, the terminal joint 

 lanceolate. Carapace slightly convex, rather broader than it is 

 long ; the front somewhat projecting, and forming, with the orbits 

 and the latero-anterior margin, a nearly regular curve, which ex- 

 tends back to a line drawn through the middle of the genital 

 region ; latero-anterior margin strongly toothed. Orbits, oval, 

 directed forwards, very open above, Avith a single fissure, both 

 in the superior and inferior margins. Eyes, smaller than their 

 peduncles. Abdomen, in the male, five-jointed ; in the female, 

 seven-jointed. 



This genus, of which one species only is at present 

 known, constitutes the nearest approximation amongst the 

 swimming Crabs, to the cancerida; the osculant genus in 

 that family which bears a near affinity to this, is Pano- 

 paus. 



