DECAPOD CRUSTACEANS OF THE WEST INDIES 35 



wet sand. Both Pachygrapsus corrugatus and P. transversus live along 

 rocky shore lines and on encrusted pilings near the tide line. Even 

 where there are comparatively few rocks, Geograpsus may seek cover 

 under various sorts of debris, its preferred habitat (see Hartnoll, 

 1965), that receives spray from breaking waves during high tides. 



In low-lying areas (pi. 4a), subject to at least occasional flooding 

 during high tides, Goniopsis cruentata, the members of the genus 

 Uca, and Ucides cordatus dig comparatively shallow burrows that 

 reach the water table. During the day, all three species may be seen 

 near the mouths of their burrows. When the latter two are disturbed, 

 they quickly scurry into the excavations they have made. The usually 

 less-abundant Goniopsis, however, apparently wanders farther from 

 its burrows and, when disturbed, may race across the mud flat or 

 seek shelter in clumps of vegetation, piles of debris, or among root 

 tangles of nearby trees. 



Among the more aquatic marine forms that venture above the 

 high-tide line are those that live on or dig burrows in the muddy banks 

 of estuaries and some that are characteristic inhabitants of mangrove 

 thickets. While Aratus pisonii is not limited to a mangrove habitat, 

 it is so frequently found climbing about the emergent portions of these 

 trees that it has been designated the "mangrove crab" or "tree crab." 

 Also frequenting the lower strata of the mangrove thickets are Eury- 

 tium limosum, Panopeus herbstii, Goniopsis cruentata, Pachygrapsus 

 gracilis, Sesarma miersii, and S. curacaoense. The latter three, however, 

 apparently are equally as much at home on the muddy banks of 

 estuaries, where they are associated with Utter or concealed in shallow 

 burrows. While members of the genus Uca are often associated with 

 these crabs along estuaries, larger colonies usually occur in tidal or 

 mud flats. Sesarma ricordi Uves among rocks and litter and sometimes 

 wanders 100 or more yards inland (see Hartnoll, 1965). 



A number of decapods in the West Indies are usually more abundant 

 in marine habitats but invade estuaries and the lower reaches of 

 streams; seldom, unless stranded, do they leave the water. Among 

 these are the young of the commercial shrimp belonging to the genus 

 Penaeus. Most of these shrimps undergo at least a part of their post- 

 larval development in estuarine and even fresh waters. (On Dominica, 

 no penaeids were observed in any of the streams, perhaps because 

 most of our observations were made during the late winter and very 

 early spring when the young have returned to the sea.) The swimming 

 crabs of the genus Callinectes frequent most estuarine habitats and 

 occasionaUy wander into fresh water. On Dominica, C. bocourti was 

 found only in the poUuted estuaries of two streams, and one was found 

 in a shallow pool, apparently stranded, on a mud flat. 



