614 BULLETIN 159, UNITED STATES NATIONAL MUSEUM 



5. Legs and caudal rami with wide basal and narrow distal portions, 



tapered to a sharp point; abdomen and second antennae 



lacking; gills of Cumacea cf ? Horaoeoscelis Hansen, 1897 



Legs and caudal rami sometimes lacking; when present cylin- 

 drical, short, bluntly rounded, and tipped with 2 or 3 setae 6 



6. Legs and caudal rami lacking; maxillipeds rudimentary, shorter 



than the maxillae; body of female flattened, wider than long; 



male unknown; gills of Crustacea $ Choniostoma Hansen, 1886 



Legs and caudal rami usually present, but rudimentary; body 



of female spherical, of male ovoid or subglobular 7 



7. Maxillipeds poorly developed, 3-segmented; caudal rami com- 



pletely fused; genital area with a large protuberance directed 



downward; on an ostracod 9 Sphaeronellopsis Hansen, 1905 



Maxillipeds well developed, 4-segmented; caudal rami com- 

 pletely separated, sometimes wholly lacking; no protuberance 

 on the genital area; marsupium of Crustacea. 



& 9 Sphaeronella Salensky, 1868 



8. Maxillipeds short and weak in female, well developed in male; 



trunk covered more or less thickly with short hairs posteriorly; 



marsupium of Crustacea cf 9 Mysidion Hansen, 1897 



Maxillipeds wanting in female, present in male, but weakly 

 developed; trunk entirely naked; first antennae short, with 

 but one segment; outside of Crustacea. 



c? 9 Aspidoecia Giard and Bonnier, 1889 



9. Macroscopic females, attached to the host 10 



Microscopic males, attached to the females 19 



10. Body elongated, symmetrical or only slightly irregular; ovisacs 



straight, cylindrical or club-shaped 11 



Body short, wider than long and very asymmetrical; ovisacs 



twisted and usually somewhat concealed 18 



11. Head produced posteriorly into a cephalic neck; antennae on 



frontal margin, mouth and mouth parts at base of neck 12 



No cephalic neck; mouth and mouth parts on ventral surface 



of head, not as widely separated from the antennae 14 



12. Head small, each lateral process tapered to a blunt point; trunk 



faintly 4-segmented; no legs, dorsal or ventral processes; 



mouth of fishes 9 Medesicaste Kr0yer, 1863 



Head larger, each lateral process broadly rounded; leg rudiments 



present; trunk distinctly divided into 2 segments 13 



13. Leg rudiments bipartite, angular, interlocked; anterior trunk 



with 2 dorsal processes, posterior without lateral processes; 



gills of fishes 9 Lernentoma Blainville, 1822 



Leg rudiments tripartite, separated; anterior trunk with 2 

 dorsal processes, posterior with 2 pairs of lateral processes; 

 gills of fishes 9 Oralien Bassett-Smith, 1899 (p. 494) 



