644 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 41. 



ridge running up from the lower edge of the carapace, and the point 

 of junction forms a prominent bUnit tooth. Posteriorly, at about 

 one-third of the length of the carapace from its hind margin, the 

 oblique ridges meet a pair of convergent longitudinal ridges separated 

 by a depression of the dorsal surface. The dorsal area enclosed by the 

 oblique ridges is flattened, with a blunt median ridge, interrupted by 



Fig. 58.— Dusttlis pi.anu'rons, female, from the .side. 



two transverse grooves just beliind the ocular lobe. The pseudo- 

 rostrum is horizontal and pointed, the lateral plates meeting in front 

 of the ocular lobe for more than twice the length of the latter. The 

 antero-lateral angle is blunt. The ocular lobe is at least as broad as 

 long and bears three well-marked corneal areas. 



The pleural plates of the second free thoracic somite are rounded and 

 rather small. The postero-lateral angles of the fifth soinite are acute 

 but very little produced. The abdomen (excluding 

 the telson) is nearly 

 equal in length to the 

 cephalothoracic re- 

 gion. The telson is 

 longer by about one- 

 third than the last so- 

 mite and about two- 

 thirds as long as the 

 peduncles of the uro- 

 pods; it is subcylin- 

 drical for about a 

 third of its length 

 from the base and 

 then narrows to the 

 slender post-anal 

 part, which, measured to the apex of the anal valves, occupies rather 

 more than one-third of its length. There are 5 pairs of rather long 

 lateral spines. 



Third maxilliped with basis expanded distally, its length along the 

 imier edge about four times its greatest width, its distal outer angle 



Fig. 59.— Diasti-lis plan- 

 ifrons, female, ante- 

 rior part of body 

 from above. 



FlG.60.— DiASTTLISPLANIFRONS, FEMALE, 

 THIRD MAXILLIPED. 



