THE GRAPSOID CRABS OF AMERICA. 375 



AcantJioplax MILNE EDWARDS, Ann. Sci. Nat., ser. 3, Zool., vol. 18, 1852, p. 



Jol [115] ; type, A. insignia Milne Edwards. 

 Enrj/chclus L. AGASSIZ, MS. label ; type, E. monilifcr L. Agassiz, MS. 



Carapace deep, subquadrilateral, with the antero-lateral angles 

 more or less produced, and the lateral borders more or less convergent 

 posteriorly, occasionally subhexagonal, broader than long, the regions 

 never very strongly defined, surface usually smooth, sometimes very 

 convex. The female is usually narrower than the male and sometimes 

 much rougher. The antero-lateral angles are very variable in indi- 

 viduals of the same species and in the two sides of the same indi- 

 vidual. This irregularity is most noticeable in the males, the side 

 of the carapace which bears the large claw being most strongly de- 

 veloped. 



Front a deflexed lobe varying in width from one-twentieth to one- 

 third of the width of the carapace and in form from narrow spatulate 

 to broad arcuate. 



The orbits occupy the remaining width of the carapace, and are 

 deep, more or less sinuous, and oblique; lower margin cut into nu- 

 merous small lobes more or less truncate, upper margin double, the 

 intervening space broad, shallow, more or less triangular; this sur- 

 face I have called the eyebrow. 



Antennulae very small; antennae of good size. 



Epistome short, distinct. Buccal cavity broader than long, side 

 margins convex, completely closed, except for a chink anteriorly, by 

 the outer maxillipeds, of which the merus is somewhat oblique and 

 bears the palpus at its antero-external angle. 



The chelipeds of the male are extraordinarily unequal, of the fe- 

 male small and equal. The large cheliped of the male is heavy, the 

 merus projects beyond the body, the carpus is subquadrilateral in its 

 external outline, the propodus and dactylus elongate and often enor- 

 mously developed. The small cheliped of the male and both chelipeds 

 of the female are similar to one another and shorter than the am- 

 bulatory legs and bear spoon-shaped fingers. Legs flattened, more 

 or less hairy, the last pair smaller than the rest. The merus joints 

 are sometimes wider in the female than in the male. A hairy-edged 

 pouch leads into the branchial cavity between the bases of the second 

 and third pairs. 



Abdomen of male usually, of female always, composed of seven dis- 

 tinct segments. In the male three or four segments may be coalesced. 1 



1 For accounts of the behavior of various species of fiddlers, see Fritz Miiller, Fncts 

 and Arguments for Darwin (translation I. London. 18<59. pp. 19, 80. etc.: also Kosmos, 

 vol. 8, 1881, p. 472 (color change) ; J. S. Kingslcy. Something about Crabs, in Aincr. 

 Nat., vol. -2-2, 1888. pp. 888-80(5; A. S. I'earso, Habits of Fiddler Crabs, in Philippine 

 Jour. Sci., vol. 7, 1912, pp. 113-133, also Smithsonian Report for 1913 (1914), pp. 

 415-428. 



