DECAPQDA. 33 



of a mean size. The external foot-jaws are approximated inferiorly 

 at their inner edge, leaving no interval between them, and their 

 third joint is transverse. 



They(l) inhabit the Eastern Ocean and the seas of New Holland. 



The following, which constitute the subgenera Gelasimus, Ocypode, 

 and Mictyris, inhabit burrows, are remarkable for the celerity of 

 their course, and have the fourth pair of feet, and next to them, the 

 third, longer than the others. The intermediate antennae are excess- 

 ively small and hardly bifid at the extremity; the radical joint is 

 nearly longitudinal. They are peculiar to hot climates. 



Here the shell is solid, of a quadrilateral or trapezoidal form, 

 widest before. 



Gelasimus, Lat. Uca, Leach. 



Eyes terminating their pedicles like a small head; third joint of 

 the external foot-jaws forming a transverse square; last segment of 

 the tail of the males almost semi-circular, that of the females nearly 

 orbicular. 



The lateral antennae are longer and slenderer in proportion than 

 those of the Ocypodes. One of the claws, now the right, and then 

 the left, varying in individuals of the same species, is much larger 

 than the other; the fingers of the small one are frequently shaped 

 like a spoon or spatula. The animal closes the entrance of its bur- 

 row, which it excavates in the vicinity of the sea-shore, or in marshy 

 places, with its large claw. These burrows are cylindrical, oblique, 

 very deep, and placed close to each other, but are usually inhabited 

 by a single individual. Their habit of holding the large claw in an 

 upright position before the body, as if making an appellative gesture, 

 has obtained for them the name of Calling-Crabs Cancer vocans. 

 One species, observed by Bosc in South Carolina, passes the three 

 winter months in its retreat without leaving it, and only visits the 

 sea when about to spawn(2). 



(1) Gonoplax transversus, Latr., Encyc. Method., Hist. Nat., ccxcvii, 2; Can- 

 cer brevis, Herbst, lx, 4. The Gonoplace de Latreille, a fossil species described 

 by Desmarest, Hist. Nat. des Crust. Foss., IX, 1 4, and perhaps also his G. 

 incise, IX, 5, 6, may be a Macrophthahnus; generally speaking, however, his fossil 

 Gonoplaces are Gelasimi. The species he calls Gelasime luisante, VIII, 7, 8, does 

 not appear to differ from the living one which I have called the maracoani, Encyc. 

 Method., lb., ccxcvi, 1. 



(2) See the article Gelasime, Nouv. Diet. d'Hist. Nat, Ed. II, and the same 

 article in the work of Desmarest on animals of that class. The Crabs, cietie-efe, 

 cietie-panama, of Marcgrave, appear to me synonymous with the Gelasimus pugi- 

 lator. According to the observations of M. Marion, communicated to the Acad. 



Vol. III. E 



