PLGET SOUND CRUSTACEA. 277 



ing on its outer or lower surface a deep groove, the anterior 

 margin of which is produced as an overlapping ridge. On the 

 inner, or in its natural position upper, face of the lamella, the 

 fold projects as a strong ridge which for part of its length is fringed 

 with digitate processes. The front edge of the second pair of 

 oostegites is received into the groove on the lower surface of 

 the first pair. The last two pairs are strongly fringed with 

 set^e on the posterior edge. 



Five pairs of biramous pleopods are present, successively 

 diminishing in size posteriorly ; those of the right side being, 

 as already mentioned, considerably larger than those of the left. 

 In the first pair the exopodite (lobe b, according to the nomen- 

 clature of Giard and Bonnier) is roughly quadrilateral in shape 

 and much smaller than the endopodite (lobe r), which is long 

 and pointed. In the posterior pairs the exopodite approaches 

 more closely in size and shape to the endopodite. The last 

 segment of the abdomen is very small and bears articulated to 

 its posterior margin a pair of lanceolate lamellae, of which the 

 right is broader and slightly longer than the left. These 

 lamellse may possibly represent the sixth pair of pleopods, but 

 a comparison with Giard and Bonnier' s figure of the correspond- 

 ing region in Palcegygc Borrci suggests that we have here to do 

 with the rudimentary pleural lamellae (lobe a of Giard and Bon- 

 nier), which, separated by a distinct suture from the fifth and 

 sixth segments in the last-named species, are here only distinct 

 on the sixth segment. If this view be adopted the sixth pair of 

 pleopods are entirely absent. In all the pleopods the surface of 

 the endopodite is roughened by irregularly transverse rugae 

 which are most distinct on the anterior pairs. 



Male. — A male individual about 3 mm. long was found under 

 the pleopods of the female. The body is symmetrical, lanceolate 

 in outline, the fourth thoracic segment being the widest. A 

 pair of eyes are present near the posterior corners of the head. 

 Both antennules and antennae are well developed, the former 

 having three, the latter five segments. As in the female, no dis- 

 tinct rudiments of the first maxillae could be identified. The 

 second maxillae have the form of rather large, rounded tubercles. 



Annals X. Y. Acad. Sci., XI, August 15, 1898 — 19. 



