148 CRUSTACEA. DECAPODA. 



FAMILY I* QUADRILATERA. 



Thorax almost square, sometimes heart-shaped, widened and 

 rounded at the anterior angles, and truncated transversely at 

 the posterior extremity ; front advanced, and more or less 

 inclined ; none of the feet terminated by a fin. 



Gen. 1. OCYPODE, Fab. Lat. Cancer, Lin. 

 Four short antennae, the intermediate ones concealed under the 

 shell ; eyes lateral, on peduncles, and below their summit ; 

 shell square, slightly flattened, with the hood narrow ; five 

 pairs of feet, the anterior pair with forceps. 



The animals of this genus inhabit the ocean. They burrow in the sand, conceal 

 themselves during the day, and run with great agility. 



O. ceratophthalmus. Fab. (C. cursor, Lin.) Shell quadrangular ; 

 ocular peduncles prolonged beyond the eyes ; forceps thick, cor- 

 diform, granulated and dentated on the edge. Inhabits Indian 

 seas. Pall. Spic. Zool. fas. 9, pi. 5. 



O. albicqns, Bosc. Shell quadrate ; peduncles of the eyes prolong- 

 ed and the point obtuse ; claws almost equal, rough with spinous 

 tubercles, and the toes short j shell whitish, shagreened, entire 

 on the margin ; last four pairs of feet white, with close hairs. 

 Inhabits coasts of Carolina. Bosc, Crust, i. pi. 4, fig. 1. 



Gen. 2, GELASIMUS, Lat. Cancer, Lin. 

 Antennae distinct, the lateral ones setaceous ; exterior feet-jaws 

 approximated ; forceps compressed, the one much larger than 

 the other ; shell trapezoidal, transverse, broadest anteriorly ; 

 eyes at the extremity of a slender peduncle. 



G. pugilator, Lat. Shell smooth, entire, sinuous anteriorly ; right 

 forceps generally larger than the left, and both slightly shagreen- 

 ed ; toes very long, bent. Inhabits Shores of Carolina. Bosc, 

 Crust, i. 197. 



Gen. 3. MYCTRIS, Lat. 



Antennae very small ; joints of the exterior feet-jaws very large, 

 foliaceous, arid hairy ; feet long ; shell suboval, truncated 

 behind, elevated ; arms at the base of the wrist bent ; forceps 

 large. 



M. longicarpus, Lat. Body subovate, yellowish, and of small size. 

 Inhabits Indian seas. Lat. Gen. i. 41. 



Gen. 4. PINNOTHERES, Lat. Cancer, Lin. 

 Antennae very short, the three first joints largest, inserted in 

 the interior corner of the eyes ; exterior feet-jaws bent, with 

 the third joint large ; forceps equal ; shell thin, flexible, or- 

 bicular, or nearly square ; eyes thick. 



The animals of this genus are in general small, and inhabit the bivalve shells of 

 the acephalous mollusca. Aristotle believed them to act as sentinels, and to guard 



