DECAPOD CRUSTACEANS OF THE WEST INDIES 69 



like cai-apace, generally dark dorsally and lighter ventrolaterally with 

 pleura distinctly lighter than terga (excluding pale markings) ; first 

 two abdominal terga with median longitudinal light stripe expanded 

 laterally in posterior portions of both, expansion on first narrower 

 but extending to base of pleura; third, fourth, and fifth terga lacking 

 median longitudinal band but each with transverse bands posteriorly, 

 those on fourth and fifth extending ventrolaterally to base of pleura 

 along posterior margins of respective terga; sixth abdominal tergum 

 with oval light patch in anterior half and much broader light area 

 posteriorly extending onto anterior half of telson. Telson and uropods 

 light (yellow, cream, or translucent) anteriorly and posteriorly A\-ith 

 dark area between; dark area on telson and inner ramus of uropod 

 covering about one-half of each, and that on outer ramus, about 

 one-quarter. Abdominal pleiu'a with irregidar markings, those on 

 second and third subtriangular with apex pointed ventrally, second 

 also with small light area antero ventrally; fourth and fifth pleura 

 each with conspicuous light areas narrow ventrally but broadened 

 dorsally. Appendages very similar to those of dark forms (see above) 

 but, by contrast, bands on legs, especially fourth and fifth, more 

 prominent. Eggs brownish red. 



Material examined. — The Dominican collections contain 177 

 males (carapace lengths 1.6-2.7 mm), 294 females (cl 1.6-4.9 mm), 

 including 144 with eggs (cl 2.8-4.9 mm), and 182 juveniles (cl 0.7- 

 1.7 mm). The smallest recognizable males, in which the appendix 

 masculina on the second pleopod varies from a barely discernible bud 

 to twice as long as the appendix interna, have carapace lengths of 1.6 

 or 1.7 mm. 



Ecological notes. — This small shrimp seems to be restricted, at 

 least on Dominica, to estuarine and sluggish lotic environments where 

 it is sheltered from rapid currents among roots of littoral vegetation, 

 in various sorts of debris, and particularly in mats of aquatic vegeta- 

 tion. The lower reaches of the Castle Bruce River are scarcely above 

 sea level, and sand has effectively impounded much of the mouth, 

 leaving only a narrow, shallow channel through which water spills 

 into the Atlantic. In the sluggish, shallow area immediately upstream 

 from the mouth there is a luxuriant growth of Potamogeton, and among 

 the mats of this plant Jonga serrei occurs in large numbers. 



The species is absent from those streams that have no estuarine 

 habitat; for example, it is not in the Rosalie River (pi. 2a), the mouth 

 of which is located only a little more than seven miles south of the 

 mouth of the Castle Bruce River and is almost continuously scoured 

 by a comparatively swift current. By contrast, Jonga has found a 

 congenial habitat among the roots of shoreline plants and in other 

 debris in the estuarine portion of the Layou (pi. 2b), the largest river 



