276 U.S. NATIONAL MUSEUM BULLETIN 271 



4. Article 5 of gnathopod 1 much longer than article 6 5 



Article 5 of gnathopod 1 shorter than or subequal to article 6 6 



5. Spines on outer plate of first maxilla nine or more, article 4 of pereopod 3 not 



wider than on pereopods 4-5 Pseudischyrocerus 



Spines on outer plate of maxilla 1 reduced to four, article 4 of pereopod 3 

 twice as wide as on pereopods 4-5 Bathyphotis 



6. Accessory flagellum a small scale, articulate or not (fig. 107c) . . Parajassa 

 Accessory flagellum elongate (figs. I07d,e) 7 



7. Coxa 5 subequal to 6 in length, coxa 1 half as long as coxa 2 . . Microjassa 

 Coxa 5 much longer than 6, coxa 1 three fourths as long as coxa 2 .... 8 



8. Pereopods subchelate (fig. lOSd) Isaeopsis 



Pereopods simple (fig. 1076) 9 



9. Outer ramus of uropod 3 with basally immersed, hooked terminal spine, 



distolateral margin of ramus with one to three large, reverted, sharp scales 

 or several denticles (fig. 108k); male gnathopod 2 usually with large tooth 

 on proximal portion of palm and with tooth on distal portion of palm. 



Jassa ^ 



Outer ramus of uropod 3 with or without basally immersed terminal spine, 



never hooked, distolateral margin of ramus with 0-7+ perpendicular, blunt, 



usually extremely small denticles (fig. 108j); male gnathopod 2 lacking 



proximal palmer tooth but often with distal palmar process . Ischyrocerus ^ 



'' These genera extremely difficult to distinguish except in adult males. 



Genera of Ischyroceridae 



Bathyphotis Stephensen 



Bathyphotis Stephensen, 1944b. 



Type-species: B. tridentata Stephensen, 1944b (monotypy). 



Accessory flagellum miiltiarticulate, elongate; article 5 of gnathopod 

 1 longer than article 6; coxa 1 more than three fourths as long as 

 coxa 2, coxa 4 subequal to coxa 6 in length, coxa 4 excavate posteriorly; 

 article 4 of pereopod 3 twice as wide as on pereopods 4-5; outer plate oj 

 maxilla 1 with jour spines {Pseudischyrocerus) . Species: 1, subarctic 

 Atlantic, bathyal (1,096 m). 



Bogenfelsia J. L. Barnard 



Bogenfelsia J. L. Barnard, 1962d. 



Type-species : B. incisa J. L. Barnard, 1962d (original designation). 



[Accessory flagellum unknown] ; article 5 of gnathopod 1 longer than 

 article 6; coxae minute, not touching, equal in length. Species: 1, 

 antiboreal Atlantic, abyssal (4,893 m). 



Bonnierella Chevreux 



Bonnierella Chevreux, 1900. 



Type-species: Podoceropsis ahyssi Chevreux, 1887 (monotypy). 



