652 THE AMERICAN NATURALIST. [VoL. XXXIV. 
£». Body symmetrical. 
h,. Posterior suckers alike in size. 
z,. Posterior region with median hooks at 
or near its posterior end; genital 
hooks with simple points. 
J, Body usually elongate ; posterior 
suckers with short stalks ; intes- 
tinal crura do not anastomose ; 
genital hooks arranged in groups ; 
vagina dorsal : on gills of marine 
fishes, especially the Clupide 
Octobothrium F. S. Leuck. (Fig. 33) 
Ją Body usually elongate, thick ; pos- 
terior suckers usually sessile ; 
genital hooks arranged in two 
lines in pairs; no vagina: on 
gills of marine fishes, especially 
the Scomberide - 
Octocotyle Dies. (Fig. 34) 
4, Posterior region without median hooks ; 
genital hooks with double points and 
arranged in a circle. 
J; Body usually elongate ; suckers at 
the end of long stalks and func- 
tioning as pincers ; vagina ven- 
tral: on gills of marine fishes, 
especially the Gadide 
Dactylocotyle v. Ben. et Hesse (Fig. 35) 
jJ» Body usually elongate ; suckers 
either stalked or not, and func- 
tioning as suckers, each sucker 
having a characteristic chitinous 
framework in form of a Greek 
cross; no vagina: on gills of 
marine fishes, especially the Spa- 
Diclidophora (Dies.) Goto (Fig. 36) 
ha. Posterior suckers not alike in size, one palT 
iffering from the others. 
i, Body elongate ; anterior pair of poste- 
rior suckers very large, at a distance 
from the others, projecting from the 
side of the body; the other three 
pairs minute, stalked, and grouped 
