416 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 99 



usual structure seen in the genus. The proportional size of the basal 

 segment is nuich less than that seen in P. columhiae. There is no dif- 

 ference in the maxilla in the two sexes (fig. 35, C) . 



The maxilliped is 3-segmented. The terminal segment is distinctly 

 tapering, ending in a rounded apex. Both second and third segments 

 bear short setae (fig. 35, D). 



The swimming legs are comparable in segmentation and ornamenta- 

 tion with the detailed formula presented for P, columhiae except for 

 two distinctive features. The marginal fringe of the first and second 

 basipodites comprises stout, conspicuous spinules rather than slender 

 cilia (fig. 36, C) . The terminal segment of the fourth endopodite pos- 

 sesses an armature of diagnostic significance. In addition to two ter- 

 minal spines, of which the medial is the longer by about a third, there 

 is a third spine, placed on the lateral margin of the segment. This 

 spine is the shortest of the three, equal to about half the length of the 

 longest. The longest spine exceeds the length of the segment (fig. 

 35, E). 



The free segment of the fifth leg is much flattened and is widest at 

 its base. Two slight convexities appear on the posterior (or medial) 

 margin. The terminal stout spine is nearly twice the length of the 

 more laterally placed seta (fig. 35, F). 



The caudal rami are very elongate, the length equaling seven times 

 the width (fig. 36, D). The proximal seta of the lateral margin is 

 placed nearly halfway from the base of the ramus to its tip. The 

 lateral distal seta is but little longer than the medial distal seta, but 

 somewhat stouter. The two central setae of the tip of the ramus are 

 jointed at the base; the longer slightly exceeds in length the caudal 

 ramus. 



The length of the body, excluding the setae of the caudal rami, is 

 2.1 mm. 



IVIale: The metasome is less elongated than in the female. The 

 urosome is 6-segmented. The rostrum, antennule, antennae, and 

 cephalic mouth parts are just as in the female. The maxillipeds are 

 of the characteristic male subcheliform construction. The basal seg- 

 ment is very wide. The second segment is less than twice as long as 

 wide. It bears a seta and a row of spines along the medial surface. 

 The terminal segment is the usual slender arc, its length exceeding 

 twice that of the second segment (fig. 36, E). 



The first three pairs of swimming legs exhibit on the distal lateral 

 corner of the second segment of the exopodite a great prolongation of 

 the integument into a large spinous process, which is differentiated 

 from a true spine by its lack of a joint or articulation with the main 

 body of the podomere. On the first leg this process equals in dimen- 

 sion the articulated spine of the distal segment (fig. 36, F). On the 



