I 90 CRUSTACEA——EUCARIDA—DECAPODA CHAP. VI 
commonly met with off the English coasts in the mantle-cavity 
of Cardium norwegicum. 
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, 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-Pacific. 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. Jlacrophthalmus, with numerous species, in 
Indo-Pacific. Gelasimus (Fig. 155), in the tropics of both 
hemispheres. Ocypoda, with similar distribution. 
1 Kingsley, Proc. Acad. Nat. Sci. Philadelphia, 1880, p. 187. 
