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U.S. NATIONAL MUSEUM BULLETIN 292 



region, smooth elsewhere; lateral margins strongly converging poste- 

 riorly, slightly concave, with acute tooth posterior to outer orbital 

 angle, fronto-orbital distance only slightly less than maximum width 

 of carapace; front curving gradually downward, neither distinctly 

 depressed nor deflexed at weak postfrontal lobes, slightly more than 

 three-fifths as wide as carapace, margin usually faintly bilobed in 

 dorsal view. Eyes well developed, cornea nearly as wide as eyestalk. 

 Ventral margin of orbit sharply produced, especially in mesial half, 

 obscurely denticulate laterally, curving abruptly to anterolateral 

 angle of mouth area. Third maxillipeds without obUque hairy ridge, 



Figure 51. — Pachygrapsus gracilis, male (carapace length 14.0 mm) from Saint Croix 



(H. A. Beatty). 



gaping, exposing mandibles. Chelipeds subequal, carpus armed w4th 

 acute distally directed tooth on flexor margin; palm with, low longi- 

 tudinal dorsal ridge or carina; fingers narrowly rounded distally, 

 spoon-tipped, movable finger compressed, rather strongly arched, 

 sharply tuberculate on extensor margin. Walking legs moderately 

 broad and flattened, merus of thkd pereiopod fully half as \vide as 

 long, with sharp subdistal tooth on extensor margin; dactyl about as 

 long as extensor margin of propodus. Denuded first pleopod of male 

 stout, terminating in posterior view in very short broadly triangular 

 corneous tip (fig. 527). A small species, maximum carapace length in 

 midline about 15 mm. 



Habitat. — Among mangrove roots and on river banks near the 



ea. 



