Phreatoicoides. 1 2 7 



pereion. They are somewhat laterally compressed, and to a very 

 slight extent deeper than the preceding ones, caused by the very 

 narrow pleura. Their inferior margins are convex and bordered 

 by a few spinules. T\\q fifth segment is three times longer than 

 any of the preceding four. The dorsal surface curves downward 

 somewhat hindward ; its anterior margin is as deep as the pre- 

 ceding segment, but the inferior margin runs upward in a 

 gradual ascent to nearly meet the dorsal surface, so that a very 

 narrow joint is formed with the sixth segment. Its inferior 

 margin is fringed like the preceding segments with scattered 

 spinules. The sixth segment (Fig. 14) is completely coalesced 

 with the telson, and measures nearly as long as the preceding 

 five segments. The dorsal surface in lateral view is slightly 

 convex, and in transverse section the sides are deeply arched 

 downwards, and the ventral surface transversely concave. The 

 middle and anterior portion is slightly wider than the posterior 

 extremity, which terminates, a short distance behind the articu- 

 lation of the basal joint of the uropods, in a widely gaping 

 abruptly truncated telson, very similar in outline, except in the 

 uropods, to P. terricola (S. and H.).^ In lateral view the 

 inferior margin, anteriorly to its insertion with the uropods is, 

 for a short distance, nearly straight and bordered by five 

 spinules ; more anteriorly it ascends in a steep grade to its 

 junction with the preceding segments, so that a triangular piece 

 appears as if cut otF from this, as also from tlie posterior end of 

 the preceding segment. The wide space thus left allows of deep 

 ventral flexion of the hind segment. At a distance of about 

 two-thirds tlie length of the segment the inferior margin ascends 

 vertically to nearly half the depth of the segment, and from this 

 part the peduncle of the uropod of each side arises, which point 

 directly hindward. The inferior margin, from the position of the 

 insertion of the superior border of the peduncle to its termination, 

 is somewhat convex in longitudinal view, and is about one-third 

 the length of the segment. From the posterior dorsal angle of the 

 telson a tuft of long fine spiniform setae point upwards and hind- 

 ward, and the posterior margin is sparsely fringed with short 

 setse. 



1 hoc. cit., p. 15. 



