DECAPOD A. GRAPSIDjE. 



BRACHYURA. 



GENUS PLANES, Leach. 



Cancer, Herbst, F.ibr. 



Grapsus, Latr. Roux, Leach. 



Planes, Leach, Bowdich. 



Nautilograpsus, Edwards, Mac Leay, Goodsir. 



Generic character. — External antenna lying at the exterior of 

 the antennary fossse, the basal articulation nearly horizontal, ex- 

 tending obliquely forwards and outwards, the outer extremity the 

 naiTOwest ; its moveable portion very short, setaceous, the joints 

 rounded. Internal antennae folded transversely in the fossae, 

 which are covered by the lamellar front, and separated by a broad 

 process extending from the epistome to the front. External pedi- 

 palps with the third joint broader than it is long, broadly and not 

 deeply emarginate at the inner half of the anterior margin. Ante- 

 rior legs robust, rounded, smooth, the hand inflated, the fingers 

 somewhat inflected, slightly toothed ; the remaining pairs much 

 compressed. Carapace depressed, convex, rounded, quadrate- 

 orbicular. Front broad, lamellar, bent somewhat downwards. 

 Orbits distant, open above. Abdomen seven-jointed in both sexes ; 

 in the male acutely triangular ; in the female, nearly orbicular. 



This genus, the only representative of the family Grap- 

 siD^ known to have been found on our coasts, has hitherto 

 been but very imperfectly elaborated. The synonymy of 

 the species is much involved, and it is almost impossible 

 satisfactorily to disentangle it. I believe there are not 

 less than three or four species, the whole of which are 

 found floating about amongst the sargasso or gulf-weed 



