40 U.S. NATIONAL MUSEUM BULLETIN 292 



of rivers should serve as barriers to the adults, the young crabs could 

 come ashore between the mouths of most of the rivers on the island. 



2. As is true for the terrestrial species, aU of the freshwater decapods 

 on Dominica except Guinotia dentata have or are believed to have 

 larval stages that require a marme habitat; consequently, as larvae 

 they can move or be transported by tides and currents around the 

 entire island, which enables the young or late larvae to gain access 

 to aU of the streams. 



3. The single decapod on Dominica that is known to complete 

 its life cycle in and around freshwater is Guinotia dentata. This crab 

 is almost as much at home in seepage areas as it is in streams, and 

 often individuals have been observed several hundred yards from 

 the nearest stream. With an annual rainfall of up to 400 inches on 

 the windward slopes of the island and with the habit of this crab to 

 wander over land, all parts of the island, except a few semixeric 

 areas such as the Grand Savane, are accessible to this species. Even 

 those streams flowing through the Savane have their headwaters on 

 the forested mountainous slopes where the crabs could safely wander 

 from one brook to another. 



Although there is no necessity for postulating that stream piracy 

 has been effective in the spread of the decapod fauna on Dominica, 

 undoubtedly it has occurred repeatedly. 



Hodge (1954), in his treatment of the flora of Dominica, presented 

 an excellent summary of the physiography, geology, soils, and climate 

 of the island and proposed a classification of the plant communities. 

 For the most part, however, the decapods do not appear to be aware 

 of the boundaries between these communities and several species 

 invade all except the "Elfin Woodland." With one possible exception, 

 none of the species on the island is limited to any one of Hodge's 

 communities. Callinectes bocourti has been found only in the lower- 

 most portions of two streams in the "Dry-Scrub Woodlands," but it 

 is highly probable that this species occurs in some of the estuarine 

 habitats along the northeast coast as well as in the Portsmouth area. 

 Where there are streams or low-lying lands, regardless of the plant 

 communities of the area, one or more decapods are almost certainly 

 present. 



Figure 3 depicts the major habitats of the Dominican decapods 

 treated herein and will perhaps be helpful for the reader in visualizing 

 the classification that follows. Basically, tliree types of decapod 

 habitats exist on Dominica: 



Marine habitats. — Despite the steepness of the submarine shore, 

 along many stretches of the coast boulders have eroded from the 

 cliffs and have fallen into the water, some with parts protruding above 

 the surface. These along wdth the man-made sea walls enable at 



