THE GRAPSOID CKABS OF AMERICA. 323 



ARATUS PISONII (Milne Edwards). 



MANGROVE CRAB; TREE GRAB. 



Plate 90. 



Aratv pinima Maecgkave de Liebstad, Hist. Rer, Nat. BrasH, lib. 4, p. 185, 



fig. in text. 

 Sesanna jnsonii Milne Edwards, Hist. Nat. Crust., vol. 2, 1837, p. TO. pi. 



19, figs. 4 and 5 (type-locality, Antilles; type in Paris Mus.). 

 Arattis insonii Milne Edwards, Ann. Sci. Nut., ser. 3, Zool., vol. 20. 18.53, 

 p. 187. 



Diagnosis. — Sides entire. Claws bristly outside. 



Description. — Carapace nearly as long as vyide; width at the level 

 of the base of the second foot three-fourths as great as width between 

 outer angles of orbit. Sides acute, entire. Regions deeply marked ; 

 outer portion of branchial regions obliquely striated, these regions 

 are also finely and densely punctate; gastric lobes and surface of 

 front rough with fine sharp granules; otherwise the carapace is 

 smooth and shining to the naked eye. 



Upper margin of front concave, its four lobes well separated, mar- 

 gined by a line of granules, inner lobes narrower than outer ; behind 

 the outer pair, another narrower pair. Front nearly vertical, about 

 four times as wide as high, sides parallel, lower edge with a broad 

 median sinus. 



Outer orbital tooth short, acute. 



Chelipeds of moderate size, palms swollen. A spine on inner mar- 

 gin of ischium. Outer face of merus and carpus covered with granu- 

 lated striae. Inner margin of arm spinulous, distal half expanded.. 

 Outer face of carpus narrow-oblong. An oval area on the outer sur- 

 face of the chelae is covered with tufts of long black bristles. Palm 

 tuberculate within and Avithout. Fingers irregularly toothed, nar- 

 rowly gaping. 



Merus joints of legs very thin and flat, a terminal and a subter- 

 minal spine above, last two joints hairy on margins, propodi elongate, 

 dactyli short. Third leg one and two-thirds times as long as cara- 

 pace, its merus a little more than twice as long as wide. 



Color. — Dark mottled green with reddish legs (Jarvis). Many- 

 colored, brow^n, blue, white, red; chelae whitish-yellow at the ex- 

 tremities (Marcgrave). 



Measurements. — Male (G434), length of carapace 21.2, anterior 

 width of carapace 22.5, width at postero-lateral angles 17.3, width 

 of front 14.8 mm. 



Hahits. — Found on mangroves, and sometimes alongshore, on 

 rocks and piles, bushes and wharves; occurs near fresh, brackish, or 

 salt water. 



