482 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxni. 



no connection across the mid-line; the rami are one- jointed and 

 rudimentary, the exopod being three times the size of the endopod; 

 they are both armed witli short spines and have no plumose setse. 



The arrangement of the spines and setse on these legs is as follows : 

 First exopod, 1,0; 4, III: endopod, 0, 0; 0, III: second exopod, 

 1, I; 4, V: endopod, 0, I; 0, VII: third exopod, 1, 0; 2, IV: endo- 

 pod, 0, 0; 0, IV: fourth exopod, 5: endopod, 2. 



Of the reproductive organs the oviducts are coiled inside the geni- 

 tal segment as in the other genera; in early stages the coils do not 

 extend much back of the base of the abdomen, but later one fold on 

 either side pushes down into the very tip of the genital segment. 

 The cement glands are considerably darker in color than the egg- 

 tubes, and are bent into a sickle shape, the concave sides facing each 

 other; the ducts leading from their posterior ends into the oviducts 

 are very short. 



The spermatophores are elliptical or slightly egg-shaped, the larger 

 end being posterior, and from it a tube leads into the vulva. At 

 first these tubes cross each other as in the other genera, but as the 

 sperms are extruded into the sperm receptacle of the female, the 

 spermatophores gradually shrivel up and each pulls across the mid- 

 line to the opposite side, so that later they present the appearance 

 seen in fig. 287. Each now stands up from the surface of the genital 

 segment in a corkscrew coil, the tip of which is nearly snow white. 

 The semen receptacle is situated just in front of the base of the 

 abdomen; it is short, curved a little, with the concave side posterior, 

 and slightly enlarged at the ends. 



Total length, 7 mm.; length of carapace on mid-line, 2.75 mm.; 

 width of same, 4.5 mm.; length of genital segment, 3 mm.; width of 

 same, 4.4 mm.; length of abdomen, 1 mm.; of egg-strings, 15 mm. 



Color, a mixture of yellow and gray, sometimes the one color pre- 

 dominating, sometimes the other. 



Male. — Carapace proportionally much larger, more than twice the 

 width of the rest of the body, and about the same length; grooves 

 and divisions as in the female. Lateral plates on the fused second 

 and third segments plainly visible just inside the posterior lobes of 

 the carapace. Dorsal plates on the fourth segment very rudimen- 

 tary, no larger than the lateral plates just mentioned, and barely 

 overlapping the base of the genital segment. 



The latter is subquadrangular, with slightly rounded sides, and 

 the posterior angles armed with sharp spines; the posterior margin 

 has a wide central sinus with divergent sides, showing most of the 

 dorsal surface of the abdomen. The margin on either side of the 

 sinus takes the shape of the letter S, almost exactly like that in the 

 genus Perissopus. The abdomen is similar to that in the female, as 

 also are the anal laminae. 



