THE GBAPSOID CBABS OF AMEEICA. 351 



Genus GECARCINUS Leach. 



Gecarcinus Leach, Edin. Encyc, vol. 7, 1S14, p. 430; type, G. ruricola 

 (Linnaeus), 



Carapace shaped much as in Cardisoma. Pterygostomian regions 

 nearly naked. Only the anterior part of the lateral border marked 

 by a marginal line. 



Fronto-orbital border half or less than half the greatest breadth 

 of the carapace. Front strongly deflexed, edge horizontal, from one- 

 fifth to one-eighth the greatest breadth of the carapace. Orbits deep, 

 not much wider than high, outer angle obtuse and not prominent, 

 inner angle a stout angular tooth which touches the front; next it a 

 deep U-shaped sinus. Eyes nearly filling the orbits. 



Antennules folded obliquely and in large part concealed by the 

 front. Interantennular septum narrow. Antennae very short, their 

 basal joint very small and not nearly reaching the front. 



A strong oblique ridge runs outward from near the extremities of 

 the epistome. 



Epistome linear, sometimes overlapped by the outer maxillipeds. 

 Buccal cavern subcircular or rhomboidal, widest at the middle; its 

 margins with a dense fringe of hair; outer maxillipeds separated by 

 a rhomboidal gape, the ischium and merus broad, of subequal length, 

 the merus suboval, concealing the short, stout palp which is attached 

 to the upper side of the middle of the distal extremity. Exognath 

 concealed and devoid of a flagellum. 



Chelipcds massive, equal or unequal, almost smooth. 



Legs stout, second pair longest, last three joints armed with spines, 

 dactyli with six or four rows. 



The seven segments of the abdomen are in both sexes separate, 

 short fringes of hair between the fourth and fifth segments of the 

 sternum, and at the extremities of the first three segments of the 

 abdomen conceal the outer end of an open channel or gutter which 

 runs along the upper side of the second abdominal segment. 



Tropical and warm north temperate America; Bermudas; Ascen- 

 sion Island ; west and south Africa ; Australasia. 



KET TO THE SPECIES OP THE CE.NOS CECABCINns. 



A*. Merus of m.nxiUipetl with entire margin. 



B\ Merus of niaxilliped distinctly longer than wide, covering the epistome 

 and antennular cavities. Dactyli of ambulatory legs armed with six 

 rows of coarse spines mricola, p. 3o2. 



B'. Merus of maxilliped about as long as wide, not covering epistome. 

 Dactyli of ambulatory legs armed with four rows of medium-sized 

 spinules, and sometimes an additional row of small spinules on the 

 upper and lower stirfaces quadratus, p. 358. 



