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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 41. 



median dorsal keel. The tergum of the fourth somite is produced 

 backward in the middorsal line, where its length is equal to that 

 of the three preceding somites together; its lateral plates are not 

 expanded, but are slightly produced downward between the coxse 

 of the third and fourth pairs of legs; each lateral plate is defined by 

 a suture line at about half the height of the somite. The fifth somite 

 has its anterior margin coarsely serrate, with rather mdely separated 

 teeth; it has a pair of dorso-lateral keels which are continued into the 

 strong, vertically compressed, slightly upturned, and acutely pointed 

 postero-lateral teeth. 



The abdomen is a little shorter than the cephalothoracic region; 

 the last somite is about half as long as the preceding. The telson 

 is half as long as the last somite, little longer than 

 broad, rounded, and quite unarmed; the tip does 

 not project beyond the anal valves. 



The antennules have the second segment of the 

 peduncle very stout, about half as 

 long as either the first or the tliird; 

 ohe inner fl.agellum has three segments 

 and is about half as long as the first 

 segment of the outer flagellum. 



The antenna is composed of four 

 distinct segments; 

 the penultimate is 

 expanded, ovate, 

 serrated on both 

 edges; the last seg- 

 ment is very mi- 

 nute and inserted 



within the margin Figs. IO4-IO6.— Colurostylis (?) occidentaus, female. 104, antenna; 

 i. . 1 T 105, THIRD maxilliped; 106, first leg. 



or the preceding. 



The mandible and other mouth parts are of normal form. The 

 third maxillipeds have the basis only slightly expanded and not pro- 

 duced at its distal angle. The ischium bears a curious comblike row 

 of short spines on its outer margin. 



The first legs have the basis, measured along the inner edge, twice 

 as long as the distal segments together; the carpus and propodus are 

 subequal, the dactylus a little shorter. The second legs have the 

 basis expanded, less than twice as long as broad, and about half as 

 long as the distal segments together; the merus is a little more than 

 half as long as the carpus, which is one and a half times as long as 

 the propodus and more than twice as long as the dactylus. 



The third and fourth pairs of legs each bear a conspicuous exopod 

 of two segments. 



