GECARCINDS. CRUSTACEA. 149 



the animal in whose shell they found protection, by warning it of approaching dan- 

 ger. 



P. pisum, Lat. Shell of the female orbicular, almost square, soft, 

 smooth, a little arched before, entire ; that of the male narrowed 

 before ; hands oblong, with a line of hairs below. Inhabits coasts 

 of Europe, in bivalve shells. B Pen. Brit. Zool. iv. pi. 1, fig. 1. 



Gen. 5. GECARCINUS, Leach. 



Four short antennae, the two intermediate ones not very appa- 

 rent ; peduncles of the eyes short and thick, and the eyes 

 subterminal ; shell cordiform, broadest and gibbous anterior- 

 ly, and truncated posteriorly ; anterior pair of legs unequal ; 

 claws and tibiae spinose. 



The animals of this genus are known under the name of Land-crabs. They pass the 

 greater part of their life under ground in holes, coming out in the evening for food. 

 Once a year, in the breeding season, they assemble in numerous troops, and take the 

 shortest direction to the sea, for the purpose of depositing their ova, and when this 

 object is accomplished return again to their haunts. It is said they stop up their 

 holes at the period of their changing their shell. When the new shell is still soft 

 they are taken as food, though this food is sometimes dangerous, from, as is suppos- 

 ed, the animal feeding on poisonous fruits. 



G. ruricola, Leach. Tarsi with six elevated serrated lines ; hands 

 smooth ; shell gibbous on the sides and above, where it is mark- 

 ed with an impression in the form of the letter H ; general co- 

 lour deep blood-red. The Antilles. Herbst, pi. 3, fig. 36. 



G. carnifex, Leach. (Ocypode, Bosc.) Shell higher and less broad 

 than the preceding, with the summit flatter and marked by an im- 

 pression like an H, prolonged before ; tarsi of the last four pairs 

 of feet with four dentated or spinous ridges ; colour reddish-yel- 

 low, with purplish lines. 3^ inches long. Inhabits the Island of 

 St Thomas, in cemeteries Herbst, pi. 41, fig. 1. 



Gen. 6. PLAGUSIA, Lat. Cancer, Fab. 

 Exterior antennae small, inserted near the origin of the ocular 

 peduncles, the intermediate ones placed in a deep cleft in the 

 head ; eyes on short peduncles ; shell flattened, almost square, 

 slightly narrowed before ; claws small, equal ; the other feet 

 strong and compressed. 



P. depressa, Lat. Shell tubercular and granular, with four teeth 

 on each side ; frontal lobes slightly projecting ; claws furrowed 

 above, terminated by a cylindrical hand, of which the fingers 

 are spoon-shaped ; colour reddish, mixed with gray. Inhabits 

 American seas. Herbst , pi. 3, fig. 35. 



Gen. 7. GRAPSUS, Lam. Cancer, Lin. 

 Four short antennae, concealed under the hood, which is entire ; 

 eyes in the lateral angles, with short peduncles ; shell flatten- 

 ed, almost square, rounded, or angular ; forceps equal, gib- 

 bous and smooth ; arms compressed above, and terminated 

 in a crest ; feet compressed, striated transversely. 



