CRUSTACEA OF NEW ZEALAND. 196 



first pair, uud bears a few seta3 at its extremity on tlie inner niarj^in ; the endopodite is 

 similar to tliat of the first pair, but bears on the inner side a long, narrow, curved 

 appendage, the " penial filament," which does not reach so i'ar as the end of the endo- 

 podite ; it appears to be semi-cylindrical, being concave on the outer side, and bears four 

 or five short setae at its extremity. Tlie portion of the endopodite between its base and 

 the base of the " penial filament " is about one-fourth the length of the whole endopodite ; 

 it is slightly enlarged, and bears toward the inner margin a powerful muscle attached 

 to the base of the " penial filament." 



It will be seen from fig. 11 that the "penial filament" of Phreatoicus assimilis, as 

 drawn, is much shorter than in P. (ludralis [20, pi. xxvi. fig. 2] ; it is, however, quite 

 probable that, like other secondary sexual characters, it may vary very greatly in deve- 

 lopment at different seasons. The exojjodite is large, and consists of two joints ; on the 

 outer side it is produced backward at the base into a rounded lobe which lies alongside 

 of the protopoditc ; the outer margin of the first joint is fringed rather sparingly with 

 short simple setae, its inner margin is straight and more thickly fringed with similar 

 setae ; the second joint is triangular, articulated to the first joint by a very narrow base ; 

 the inner margin is straight, and, like that of the first joint, is fringed with simple setae, 

 but these are much longer than on the first joint ; the extremity, which is oblique, is 

 bordered on the outer margin by about 10 long delicately plumose setae. 



The endopodite does not hang by the side of the exopodite, but overlaps it, and the 

 exopodite is curved so as to receive it ; a raised ridge runs from the outer extremity of 

 the protopodite toward the outer margin of the fii-st joint of the exopodite, meeting it 

 at about the middle, and thus bordering the depression within which the exopodite lies. 

 The endopodite usually overlaps the exopodite to a greater extent than is shown in 

 fig. 11, where it was purposely somewhat separated from the exopodite to allow the 

 form of the latter to be more clearly seen. The more natural position of the two is 

 shown in fig. 12, which represents the third pair of pleopoda. 



I have had no opportunity of examining the pleopoda of a female specimen of 

 Fhreatoicns assimilis, but from the analogy of P. australis and P. typicus I have no 

 doubt that the second pleopoda would resemble that of the male, as above described, 

 except that there would be no penial filament. 



The third pair of pleopoda (tig. 12) are similar to the second, but the endopodite is 

 rather smaller in proportion to the eaopodilc, and does not reach beyond the base of the 

 second joint of the latter. From the outer margin of the protopodite arises a sub- 

 triangular lobe projecting nearly at right angles to the protopodite, and apparently 

 representing the epipodite ; its margins bear long simple setae, widely separated from 

 each other, and its integument, though apparently thicker than that of the rest of the 

 pleopod, is more or less membranaceous, so that this epipodite is perhaps also branchial 

 in function. 



The significance of the occurrence of an epipodite in the pleopoda of Phreatoicus is 

 considered later on (see p. 214). 



The fourth and fifth pairs of pleopoda contain precisely the same parts as the third 

 pair, but each is much shorter and broader than the preceding. 



SECOND SERIES. — ZOOLOGY, VOL. VI. 26 



