196 CRUSTACEA EUCARIDA DECAPODA CHAP, vi 



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

 of Cardimn nor<n'i/i<-//m. 



Fam. 4. Grapsidae. 1 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. 

 Ses'arma, with fresh-water and land representatives in the tropics 

 of both hemispheres. Cydograpsus, marine 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. Cardisoma is a completely circumtropical genus, 

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

 throughout the Indo-Paclfic. Gecarcinus 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 hemisphere they extend far into the 

 temperate regions. Macrophthalmus, with numerous species, in 

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

 hemispheres. Ocypoda, with similar distribution. 



1 Kingsley, Proc. Acad. Nut. ,sv/. Philadelphia, 1880, p. 187. 



