30 PKOCEEDINGS OF THE NATIONAL. MUSEUM VOi>. 82 



7. Terminal segment of left exopod of male fifth foot truncated 8 



Terminal segment of left exopod of male fifth foot either 



rounded or armed with a number of spines 9 



8. Terminal segment of left exopod of male fifth foot dentate at 



distal margin and having an acute spine at inner distal angle. 



richardi (Dahl) 

 Terminal segment of left leg exopod of male fifth foot setose on 

 distal margin and armed with a short, stout spine at inner 



distal angle cristobalensis Marsh 



P. Terminal segment of left exopod of male fifth foot rounded at 



distal end culehrensis Marsh 



Terminal segment of left exopod of male fifth foot armed 



with spines 10 



10. Left endopod nearly as long as exopod; abdomen of female 



4-segmented coronatus Williams 



Left endopod only slightly longer than first segment of exopod ; 

 abdomen of female 3-segmented pelagicus Herrick 



PSEUDODIAPTOMUS ACUTUS (Dahl) 



Pl^te 15, Figures 1. 2. 4 



WeismaneUa acuta Dahl, 1894, pp. 10, 11. pi. 1, figs. 9-11. 

 Pseudodiaptomus acutus Giesbeecht and Schmeil, 1898, p. C'-i. 



Female. — The head is not distinctly separated from the thorax. 

 The last tAvo thoracic segments are armed, on the posterior border, 

 with small spines, and the wings of the last segment are pointed. 

 (PI. 15, fig. 1.) There are spines on the posterior borders of the 

 first three abdominal segments. The abdomen has four segments. 

 The first antennae have 21 segments and extend to the second ab- 

 dominal segment. In the fifth feet (pi. 15, fig. 4) the terminal hook 

 is about twice as long as the third segment of the exopod. The 

 inner spine of the second segment of the exopod is broad and ciliate. 



Length, 1.3 mm. 



Male. — In the fifth feet (pi. 15, fig. 2) there is a small endopod on 

 the left foot. The terminal segment of the left foot is short and 

 dentate on its distal border. The second segment of the basipod of 

 the right foot has hairs along its inner border. The first segment 

 of the exopod of the right foot has a linguiform appendage on its 

 inner distal border. 



Length, 1 nun. 



Occv/prence. — Found in the mouth of the Amazon in brackish 

 water. 



PSEUDODIAPTOMUS AUEIVILLI Cleve 



Plate 15, Figures 3, 5-7 



Pseudodiaptomtis aurivilU Cleve, 1901, pp. 48-50, pi. 6, figs. 11-22. — Thompson 

 and Scott, 1903, p. 248, pi. 2, figs. 24-26.— A. Scott, 1909, p. 116.— Sewell, 

 1912, p. 363. 



Pseudodiaptomus mertoni Feuohtl, 1923, p. 455, figs. 23. 24. 



