620 BULLETIN 159, UNITED STATES NATIONAL MUSEUM 



58. Body an ellipsoid, its frontal margin squarely truncated; distal 



end of trunk on this margin beside mouth parts; gills of fishes. 



cf Clavellodes Wilson, 1915 (p. 516) 

 Body an ovoid, its frontal margin very oblique; distal end 



of trunk considerably behind mouth parts 59 



59. No dorsal carapace or genital process; first antenna 2-seg- 



mented; second antenna uniramose, 3-segmented; first 

 maxilla small, bipartite; gills of fishes, cf Clavella Oken, 1815 (p. 513) 

 A distinct carapace and genital process; first antenna 3-seg- 

 mented; second antenna biramose, the rami 1-segmented; 

 first maxilla tripartite; gills of fishes, cf Clavellisa Wilson, 1915 (p. 517) 



60. Macroscopic females, attached to host 61 



Microscopic males, attached to females 77 



61. Head or neck, or both, with horns or processes for anchoring 



the copepod; some of the segmented appendages present 62 



Head and neck greatly modified and fused with tissues of host, 



with a chitin anulus; no horns or appendages 66 



62. Posterior processes cyUndrical, smooth, each 3-segmented; 



neck twisted, with short chitin processes; head much wrin- 

 kled; flesh of fishes 9 Periplexis Wilson, 1919 



Posterior processes cylindrical, smooth, not segmented; neck 



and head smooth, sometimes with soft horns or processes 63 



Posterior processes covered with many cones or cylinders; neck 



smooth, bent but not twisted, with processes or horns 65 



63. Head orbicular, neck stout, depressed, neither of them with 



horns or processes; 2 long posterior processes on trunk; gill 



cavity of sharks ? Opimia Wilson, 1908 



Head with conspicuous processes or horns 64 



64. Head with 3 pairs of globular processes; neck slender, cylin- 



drical; 2 posterior processes dorsal to egg strings; gill cavity 



of sharks ? Paeon Wilson, 1919 (p. 524) 



Head with stiff cartilaginous horns; neck filiform, widened 

 posteriorly; 2 posterior processes ventral to egg strings; 

 gills of fishes ? Trypaphylum Richiardi, 1878 



65. Head a narrow cylinder, with lateral processes at posterior end; 



neck filose; posterior processes covered with cylinders; 



flesh of fishes 9 Rebelula Poche, 1902 (p. 528) 



Head wide with enormous lateral processes; neck stout; 

 posterior processes dichotomously branched; no cylinders; 

 flesh of fishes 9 Sphyrion Cuvier, 1830 (p. 530) 



66. Body of female distinctly segmented; annulus ^^ ventral; male 



a pygmy, not segmented, with 2 pairs of antennae and 1 pair 



of mouth parts; skin of annelids 9 Melinnacheres M. Sars, 1870 



Body of female distinctly segmented; annulus terminal; male 



unknown; skin of annelids 9 Oestrella Mcintosh, 1885 



Body of female without any trace of segmentation 67 



67. Neck with a well-defined annulus,^^ the head and neck often 



incapable of separation from tissues of host 68 



No neck or annulus, ^^ the anterior portion of trunk fused directly 



with tissues of host 76 



68. Body of female twice as long as wide, or even longer 69 



Body of female about the same length and width 72 



Body of female definitely wider than long 74 



2» A chitin ring at the base of the neck where it joins the trunk. 



