798 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



The 5 arms reach a length of 125 mm. in the largest specimens. Their structure 

 is the same as that of the arms of P. varians, but they are generally stouter and more 

 robust than in that species. 



Syzygies occur between brachials 4 + 5, 9 + 10 or 10+11 and distally at intervals 

 of from 2 to 6 (usually 4 or 5) muscular articulations. 



PI and P a are absent. The remaining pinnules resemble those of P. varians. 



[NOTES BY A.M.C.] The syntypes of japonicus in the British Museum have the 

 centrodorsal relatively large. In one (fig. 50, a), it is distinctly conical and is 3.7 mm. in 

 basal diameter and 3.0 mm. high. In the other, the shape is more hemispherical and 

 the diameter is 3.8 mm. but the height only 2.4 mm. The sides of the centrodorsal 

 are covered with about three irregular rows of cirrus sockets, numbering XL in one 

 specimen and XXXV in the other. The peripheral sockets particularly have the rims 

 very prominent, projecting out from the surface. According to Carpenter the cirri 

 were tapering and more than 35 mm. long with 27 segments. Only a fragment of one 

 now remains. 



The proximal brachials are considerably expanded at the joints, except for the 

 syzygies, which are constricted so that the first one is only 1.8 mm. wide, i.e., the same 

 width as in the types of P. semperi where the brachials are straight-sided and appear 

 much less robust. The second syzygy is either at bracbials 9 + 10 or 10 + 11; in the 

 former case the first nine brachials together measure 10.0 mm. in both specimens. 

 The lowest pinnules appear to be fairly equal, with about 20 stout segments, of which 

 the proximal ones are short. The following pinnules develop relatively longer and 

 more slender segments. 



The disk appears to be naked. The brachial ambulacra have a few supporting rods 

 and fenestrated plates. There are no sacculi. 



Some numerical details of these and certain other specimens are included in 

 table 18 (p. 802). 



In a relatively small specimen from Albatross station 4900 (fig. 50, c), P 2 and P 3 are 

 similar, with 25 to 30 segments, of which the longest proximal ones are about two and 

 a half times as long as broad but the distal ones are relatively shorter, not longer than 

 broad. The cirri differ from those of larger specimens in having the penultimate seg- 

 ment shorter than the preceding one and the terminal claw curved and acute. 



Of the Siboga specimens, the one from station 38 has three or four of the basal 

 cirrus segments not longer than broad and the longest segments are about three and 

 a half times as long as broad. The specimen from station 74 has an incomplete cirrus 

 of 34 segments, probably two or three more when complete. The suture of the first 

 syzygy is distinctly diagonal and the fourth brachial in each case has a lateral projection. 



Notes. Of the 80 specimens collected by the Albatross off Southern Japan 

 in 1906 the largest (with the arms 125 mm. and the cirri 54 mm. in length) were from 

 station 4958, where P. varians was not found; but examples from station 5083 were 

 nearly as large (with the arms 100 mm. and the longest cirri 42 mm. long) and were 

 here associated with the largest individuals collected of the other species. Medium- 

 sized specimens were dredged at stations 4903, 4916, 4919, 4975, 4976, 4980, 5079, and 

 5082, and small ones only at station 4900. 



