406 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxni. 



versely elliptical, the sides and frontal margin forming a very even 

 curve. Frontal plates considerably enlarged at the outer ends and 

 nearly covering the basal joints of the first antennae. Posterior 

 lobes wide, triangular, quite sharply pointed, and curved strongly 

 inward toward the free throax; their tips reach a little beyond the 

 center of the third thorax segment, and if straight would probably 

 reach its posterior margin. 



Grooves separating the cephalic and lateral areas extending for- 

 ward visibly to the anterior margin just behind the base of the first 

 antennae. Posterior margin between the lobes nearly straight, with 

 no traces of spines or teeth; secondary lobes elliptical, considerably 

 longer than wide. Eyes visible in the younger specimens close to 

 the mid-line, one-third the distance from the anterior margin of the 

 carapace; invisible in mature adults. The three free segments 

 together one-fourth shorter than the carapace, the second segment 

 one-thn'd wider than the other two, which are about equal. The 

 lateral appendages of tliis segment are very oblique and are partially 

 covered by the accessory posterior lobes of the carapace. 



The sides of the third and fourth thorax segments project a dis- 

 tance equal to half their length and are evenly rounded, giving the 

 segments an elliptical form, transversely elongated. 



Genital segment flat and somewhat elongate, narrowed into a neck 

 anteriorly where it joins the fourth segment, and carrying two pairs 

 of lobes posteriorly. The larger pair are triangular and situated at 

 the posterior corners; the smaller pair are just in front of them, on 

 the sides of the segment. 



The latter are armed on their ventral and inner margins with 

 small spines and setae and are evidently the rudimentary fifth legs. 

 The sixth legs, however, are not on the posterior lobes, but inside 

 of them on the posterior margin of the segment, between the lobes 

 and the abdomen. They are well shown in this position by both 

 Steenstrup and Liitken and Kroyer. 



Abdomen two-jointed, joints the same length, but the basal one is 

 somewhat the wider, with strongly convex sides and a slight notch 

 at the center of the posterior margin. Terminal joint with an anal 

 incision which reaches nearly to its base, and with its posterior margin 

 straight or only slightly oblique. 



Anal lamina? large, four-fifths as long as the entire abdomen and 

 three-fifths as wide, each armed with four setae, of which the inner one 

 is considerably the smaller, is removed a little from the other three, 

 and is abruptly curved inward near its base. 



First antennte minute and not heavily armed with setae; the 

 terminal claw of the second pair abruptly bent near its tip and 

 armed with two accessory claws on its inner surface. 



