418 PROCEEDINGS OF THE NATIONAL MUSEUM vol.99 



tions comprise very long toothlike shreds of the integument, arranged 

 roughly as alternate wide and narrow spinules (fig. 36, H) . 



The egg sacs are elongate in this species, reaching to the caudal 

 rami. The eggs are large. Each ovisac contains about 30 eggs. 



The rostrum and antennules conform very closely to the condition 

 figured for P. panopeae. The terminal segments of the antennule 

 exhibit a slight degree of specific differentiation, however ; in P. tivelae 

 the sixth segment is longer than the fifth ; in P. panopeae the propor- 

 tion is reversed. 



The antenna conforms almost exactly in proportions to that of P. 

 columbiae. 



The mandible is a very generalized one, its gradual taper and very 

 simplified ornamentation of marginal cilia suiting it to exemplifica- 

 tion as the typical form of the appendage for the genus or even for 

 the family (fig. 36, I). The maxillule differs only in subtle and in- 

 significant particulars of outline from that already illustrated for P. 

 coJwnhiae. It is a simplified, flat, tapering plate with two terminal 

 setae. The maxilla, like the mandible, may be considered as general- 

 ized in construction (fig. 36, J). The well-developed base does not 

 show the extreme enlargement that characterizes this appendage in P. 

 columhiae. In the present species, the length of the basal segment 

 but little exceeds its width. The terminal segment differs from the 

 other species in the present collection by the lack of ornamentation of 

 the more distal of the setae on the anterior surface. In the other 

 species there are fine spinules or cilia arranged along one or both 

 margins of the seta. Such simple setae are found in this position in 

 some other members of the genus. In all the species, the more proxi- 

 mal of the two setae of this segment is always without ornamentation. 



The maxilliped is distinctive in P. tivelae (fig. 36, K) . The articu- 

 lation with the head is so complicated that it is impossible from my 

 preparations to say with certainty whether the appendage is 2- or 3- 

 segmented. The terminal segment is conical, with pronounced round- 

 ing of the tip. This segment bears two minute setae. The segment 

 next proximal (basal segment?) is subquadrate, of very great width 

 in proportion to its length. 



The swimming legs are all by generic definition 3-jointed in both 

 rami. The number and distribution of the spines and setae are ex- 

 actly those presented above for P. columhiae. Characteristic minor 

 features of these limbs for the species are the following, however : The 

 basipodite of the first legs bears a marginal fringe of very stout 

 spinules (as illustrated for the male of P. panopeae). On the bases of 

 all the other legs, this fringe is comprised of well-developed cilia, much 

 more slender and delicate in configuration than the robust spinules, 

 although of about equal length. Very stoutly developed spinous proc- 



