622 BULLETIN 159, UNITED STATES NATIONAL MUSEUM 



78. Head with large swelling on dorsal surface at each side; trunk 



distinctly segmented, the segments increasing in size back- 

 ward; flesh of fishes d" Rebelula Poche, 1902 (p. 528) 



Dorsal surface of head without sweUings; entire body dis- 

 tinctly segmented and cyclops-like 79 



Dorsal surface of head without sweUings; anterior body only 

 segmented, posterior portion completely fused 81 



79. Metasome 2-segmented, urosome 2-segmented; first antennae 



3-segmented; second antennae mere knobs; 2 pairs biramose 



legs, the rami 1-segmented; on Crustacea cf Rhizorhina Hansen, 1892 



Metasome 4-segmented, urosome 3-segmented; 3 pairs of bira- 

 mose legs SO 



80. A fold between rostrum and head; no first antennae; rami of 



all 3 pairs of legs 1-segmented, exopods broad laminae; on 



annelids c? Sarsileniura Leigh-Sharpe, 1926 



No fold between rostrum and head; first antennae 3-seg- 

 meuted; exopods of first and second legs 2-segmented, endo- 

 pods and third leg rami 1-segmented; on annelids. 



c? Herpyllobius Steenstrup and Liitken, 1861 



81. Head with a carapace; first free segment well defined; first 



antennae 3-segmented; caudal rami each tipped with a spiny 



seta; gill cavity of sharks cf Paeon Wilson, 191:9 (p. 524) 



Head without a carapace; first free segment fused with trunk; 

 first antennae indistinctly segmented; caudal rami without 

 setae; gills of fishes cf Trypaphylum Richiardi, 1878 



82. Body of female segmented faintly or not at all, without pro- 



cesses; no part of body conspicuously enlarged 83 



Body of female distinctly segmented, but no part conspicu- 

 ously enlarged; metasome and often urosome with soft paired 



processes 85 



Body of female distinctly segmented, one part conspicuously 



enlarged, the rest much smaller, with or without processes 89 



Body of male harpactoid, attenuate, distinctly segmented; 2 

 pairs of biramose legs ; 2 pairs of antennae 92 



83. Three pairs of leg rudiments, first 2 biramose; 2 pairs antennae, 



second pair only prehensile; 2 pairs mouth parts; body 



unsegmented; scales of fish 9 Iiernaeascus Claus, 1887 



No leg rudiments, but body distinctly segmented; no processes 84 



84. Body cylindrical, smooth; 2 pairs of antennae, both prehensile; 



2 pairs of mouth parts; a bilobed rostrum curved ventrally; 



mesogloea of polyps 9 Mesoglicola Quidor, 1906 



Body ovoid, covered with small papillae; 3 pairs of rudimentary 

 mouth parts, but no antennae and no rostrum or ovisacs; 

 flesh of fishes 9 Sarcotaces Olsson, 1872 



85. One pair of soft dactylose dorsal processes on fifth segment; 



rudimentary antennae and mouth parts; 2 pairs biramose 



legs; in ascidians 9 Antheacheres M. Sars, 1870 



Three to six pairs of lateral processes on metasome only 86 



Fifteen pairs of soft lateral processes, on metasome and uro- 

 some, 2 pairs branched; no antennae, mouth parts, or legs; 

 frontal sinus of fishes 9 Philichthys Steenstrup, 1862 (p. 531) 



