196 CRUSTACEA — ^EUCARIDA DECAPODA chap, vi 



commonly met with off the English coasts in the mantle-cavity 

 of Cardium nonrrf/inn/i. 



Fam. 4. Grapsidae.^ — Carapace square, the lateral margins 

 either strictly parallel or slightly arched. The orbits and eyes 

 are moderately large, but the eye-stalks are not much lengthened. 

 Littoral, fresh -water, and land. Pachygrapsus marmoratus 

 (Fig. 134), the common shore - crab of the Mediterranean, 

 Sesarma, with fresh-water and land representatives in the tropics 

 of both hemispheres. Cyclograpsus, inarine in the tropical 

 littoral. 



Fam. 5. . Gecarcinidae. — Carapace square, but much swollen 

 in the branchial region. Orbits and eyes moderately large. 

 Typically land forms, which only occasionally visit the sea or 

 fresh water. Canlisohia is a completely circumtropical genus, 

 with species in tropical America, West and East Africa, and 

 throughout the Indo-Pacific. Gecarcimis in West Indies and 

 West Africa,. 



Fam. 6. Ocypodidae. — Carapace square or rounded, generally 

 without teeth on the lateral margins. The orbits transversely 

 lengthened, eye-stalks usually very long. The members of this 

 family generally inhabit the mud-flats and sands of tropical 

 coasts ; in the southern liemispliere they extend far into the 

 temperate regions. Macrojjhthalmus, with numerous species, in 

 Indo-Pacific. Gelasimus (Fig. 135), in the tropics of both 

 hemispheres. Ocypoda, with similar distribution. 



^ Kingsley, Proc. Acad. Nat. Sci. Philadelphia, 1880, p. 187. 



