ART. 18 SYNOPSIS OF CALANOID CRUSTACEA MAESH 35 



on its inner margin and a hair on the posterior surface near the 

 inner distal angle. The second segment of the exopod is about equal 

 in length to the first, is curved, its outer margin being convex and its 

 inner concave, and is armed with three blunt spines. The endopod 

 is elongate, of one segment, rounded at the distal end and longer than 

 the first segment of the exopod. 



Length, 0.88 mm. 



Occm^ence. — Found in Rio Culebra, a branch of the Eio Chepo in 

 Panama. Dodds (1926) reported it from Miraflores Lake. This is 

 the only species of PseudodiaptoTnus that has been found on the 

 Pacific coast of America. 



PSEUDODIAPTOMUS GRACILIS (Dahl) 



Plate IS, Figxjres 4-6 



Weismanella gracilis Dahl, 1894, p. 11, pi. 1, figs. 12-14. 



Pseudodiaptomus gracilis Giesbrecht and Schmeil, 1898, p. 65. — Weight, 1928, 

 pp. 589-592, figs. 1, 2. 



Female. — Head and thorax not clearly separated. Last thoracic 

 segment rounded, without spines. The abdomen (pi. 18, fig. 6) con- 

 sists of four segments. There are processes on each side of the gen- 

 ital aperture. There are spines on the distal margins of the first 

 three segments. The f ureal rami are rather short, about four times as 

 long as broad, and ciliate on the inner margins. The first antennae 

 have 20 to 22 segments. Dahl figures 20, and Giesbrecht and Schmeil 

 give the same number ; Wright gives 22 ; the author has found some- 

 times 20 and sometimes 22. The antennae reach the end of the first 

 abdominal segment. In the fifth feet (pi. 18, fig. 4) the two basal 

 segments and the first exopod have minute spines on their distal 

 borders. There is an acute spine at the outer distal angle of the 

 second segment of the basipod and a rather stout curved spine at the 

 similar position on the first segment. The second segment of the 

 exopod has a strong spine about midway of its outer border. The 

 terminal hook is slender, falciform, and finely dentate on its inner 

 border. At its base is an acute, curved dentate spine; this is the 

 typical inner spine of the genus. The usual spine branching from 

 the base of the hook is, in this species, a slender acute spine applied 

 closely to the hook. It is not shown in Figure 4. 



Male. — The fifth foot of the male (pi. 18, fig. 5) has no endopods. 

 The second segment of the basipod of the right foot has hairs on 

 the inner border. The first segment of the exopod has long stiff 

 hairs on its inner border and the outer distal angle is prolonged into 

 a hooklike spine, which nearly reaches the end of the second segment. 

 The second segment of the exopod has an acute spine at about two- 



