368 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 115 



The female genital segment of D. ulua has distinct posterior lateral 

 lobes. That of D. curtus has two sets of distinct knobs on the pos- 

 terior sm-face, the posterior lateral of which may be compared to the 

 posterior lateral lobes of D. ulua. 



The fifth and sixth legs of the male members of the genus determine 

 at least part of the shape of the segment, due to the association of the 

 legs with the segment. Because of this, no distinct similarities or 

 differences can be shown without discussing the fifth and sixth legs. 



The female fifth leg (figs. I2a-d) is long and possesses a short 

 terminal process in both D. ulua and D. hijurcatus and is long and 

 possesses a long and well-developed terminal process in both D. curtus 

 and D. litus. The only major difference between the female fifth leg 

 of D. curtus and that of D. litus is that the terminal process of D. curtus 

 is naked while that of D. litus is plumose. 



The male fifth leg (figs. 12e-h) of D. bifurcatus is s^ikelike while th&t 

 of D. curtus and D. litus is similar, in general makeup, being rather 

 stocky, with a scoop-shaped distal end which gives rise to a naked 

 terminal process in D. curtus and a plumose process in D. litus, as in 

 the female. The fifth leg of D. ulua is much longer than that of 

 D. curtus and D. litus but, like them, has a scoop-shaped distal end 

 which gives rise to a short process that, in D. ulua, is plumose. 



The male sixth leg (figs. 12i-Z) of all four species is short and, in 

 D. ulua and D. hijurcatus, is of a more generalized nature than the 

 fifth leg. The sixth leg of D. ulua is knob-shaped while that of 

 D. hijurcatus is spikelike, although with a broad base. The sixth leg 

 of both D. curtus and D. litus is short and generally knob-shaped but 

 has a scoop-shaped distal end similar to that of the fifth leg. The 

 distal end of the sixth leg of D. curtus bears two naked, setalike 

 processes and one plumose seta while that of D. litus bears two plumose, 

 setalike processes. 



The abdomen of all four species is 1-segmented. The female of 

 D. curtus possesses an abdomen with a distinct lobate projection on 

 each posterior lateral surface, while the female of the other three 

 species has either a flat posterior sm-face, except for the anal indenta- 

 tion, or a biconcave posterior surface which forms the attachment 

 and articulation sm-face for the caudal rami. 



The caudal rami of all four species are fairly similar and do not 

 present differences that appear sufficient to warrant any specific 

 comment. 



The antennule appears to present relatively few comparable charac- 

 teristics, with the exception of one, that of the projection of the 

 posterior distal surface of the first segment present in D. hijurcatus, 

 D. curtus, and D. litus. This projection is heavily sclerotized and, 

 in D. hijurcatus, is small and knob-shaped while in both D. curtus and 



