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BULLETIN 201, UNITED STATES NATIONAL MUSEUM 



is long and narrow, about three times as long as broad. The exopod 

 is likewise rather long and narrow compared with other members 

 of the group Mysida. 



Figure 4. — Petalophthalmus armiger Willemoes-Suhm : a, Right mandible, X 24%; b, left 

 mandible, X 24%; c, maxillule, X 24%; d, maxilla, X 24%; e, endopod of first thoracic 

 limb, X 24%;/, first pleopod of male; X 10%; g, second pleopod of male, X 10%. 



The first thoracic limb (fig. 4, e) (maxilliped) has a small but dis- 

 tinct gnathobasic lobe on the second joint and the large lobe from the 

 fourth joint appears to be more pointed and narrower than is figured 

 by Sars (1885), and terminates in a single strong spine. There is a 

 well-developed epipodite present on this appendage. Sars (1885) 

 stated that it was absent. 



I have nothing to add to the existing descriptions of the remaining 

 thoracic appendages, except to note that the last thoracic limb of the 

 male has a well-developed genital appendix of the normal mysidacean 



