160 BULLETIN 201, UNITED STATES NATIONAL MUSEUM 



Telson cleft, the cleft armed with teeth and a pair of plumose setae, 

 lateral margins armed with spines along the whole length. 



First, second, third, and fifth pleopods of the male simple un jointed 

 plates as in the female; fourth pleopod of the male consisting of 

 sympod and endopod only, the exopod absent ; endopod fused with the 

 second joint of the sympod, elongate and multiarticulate, terminal 

 joint armed with two spines (or modified setae) . 



Remarks. — The systematic position of this genus is obscure. Un- 

 fortunately the single specimen is immature, and the full elucidation 

 of its systematic position must await the advent of fully grown speci- 

 mens. The fourth pleopod of the male is unique if my interpreta- 

 tion of the immature appendage is correct. The exopod appears to 

 be completely absent and the endopod to be fused with the second 

 joint of the sympod. I have interpreted the single ramus as the endo- 

 pod because it bears at its base the usual side lobe, which is more or 

 less characteristic of the endopods of the male pleopods in Mysidae. 

 In this genus the endopod is elongated and composed of 14 joints 

 altogether including the fused basal joint and sympod. I know of 

 no other mysid that has the fourth pleopod of the male of this type. 

 In those Mysidae in which the fourth pleopod of the male is modified 

 it is usually the exopod which is the elongate and modified ramus. 



INUSITATOMYSIS SERRATA, new species 



Figure 60 



Description. — Carapace leaving the last thoracic somite completely 

 uncovered and the penultimate somite uncovered in the middorsal 

 line ; produced in front into a short triangular rostral plate, obtusely 

 rounded at the apex and leaving the eyes and eyestalks completely 

 uncovered; the front margin is also slightly produced into a small 

 spine on each side to the outside of the eyestalks ; anterolateral corners 

 rounded. 



Eyes very large, reniform, depressed dorsoventrally, extending for- 

 ward almost to the end of the second joint of the antennular peduncle, 

 cornea occupying more than half the entire eye in dorsal view, a small 

 blunt tubercle on the dorsal side of the eyestalk, pigment golden- 

 brown. 



Antennal scale (fig. 60, a) extending forward beyond the distal end 

 of the antennular peduncle by about one-fifth its length, three and a 

 half times as long as broad, outer margin not setose but terminating 

 in a strong spine and provided with five strong teeth in addition to 

 the terminal spine; apex of the scale produced beyond the terminal 

 spine of the outer margin into a lobe which is as broad as long; no 

 distal suture. 



