A REVIEW OF THE MYSIDACEA 35 



Suborder Mysida 



Carapace generally small, its posterior part generally leaving one 

 or more of the thoracic somites exposed ; second pair of thoracic limbs 

 modified as gnathopods; no branchiae on any of the thoracic limbs; 

 oostegites of the female sometimes seven pairs but mostly only two 

 or three pairs; pleopods in the female generally rudimentary and 

 not natatory ; pleopods of the male sometimes biramous and natatory, 

 more often one or more pairs modified as accessory copulatory organs. 



Family PETALOPHTHALMIDAE Czerniavsky 

 Petalophthalmidae Czerniavsky, 1882a, p. 56. 



Maxillule without palp ; first thoracic limbs without exopod ; second 

 thoracic limbs with a lamellalike expansion of the merus ; penultimate 

 joint of the endopodites of the third to the eighth thoracic limbs 

 not jointed; seven pairs of oostegites; pleopods of the female slender, 

 biramous or uniramous; pleopods of the male robust, biramous, 

 natatory ; no statocyst on the inner uropods. 



Four genera have been referred to this family, Ceratomysis, 

 Hansenomysis, Petalophthalmus, and Scolophthalmus, of which the 

 first three are represented in the National Museum collection. 



Genus PETALOPHTHALMUS Willemoes-Suhm 



Petalophthalmus Willemoes-Suhm, 1874a, p. xiv; 1875, p. 40. 



PETALOPHTHALMUS ARMIGER Willemoes-Sohm 



Figures 3, 4 



Petalophthalmus armiger Willemoes-Suhm, 1875, p. 44, pi. 7. — G. O. Sars, 1884, 

 p. 34 ; 1885, p. 174, pi. 32, figs. 1-9.— Faxon, 1895, p. 221 ; 1896, p. 164.— Holt 

 and Tattersall, 1906b, p. 22.— Tattersall, 1911, p. 25; 1925, p. 4, pi. 1, figs. 

 1-3 ; 1939a, p. 229.— Hansen, 1927, p. 22, pi. 1, fig. 6a. 



Petalophthalmus paciflcus Faxon, 1893, p. 218 ; 1895, p. 223, pi. 54, figs. 1-le. — 

 Ortmann, 1905, p. 971. 



Occurence. — Caribbean Sea : Albatross station 2140, 2 adult fe- 

 males, 36 mm. Bering Sea : Albatross station 3308, 1 adult male, 48 

 mm. California: Albatross stations 4390, 1 female, 50 mm.; 4544, 

 1 female, 42 mm. 



Distribution. — Tropical Atlantic, 2,500 fathoms {Challenger) ; Gulf 

 of Mexico, 955 fathoms (Faxon) ; west coast of Ireland, 900 to 1,200 

 fathoms (Holt and Tattersall, and Tattersall) ; off the coast of Mo- 



