650 THE AMERICAN NATURALIST. [Vor. XXXIV. 
e, Anterior glandular areas large and prominent, one on 
each side of anterior end. 
f, Body elongate ; sucking disk nearly circular and 
containing one central, eighteen peripheral, and 
seven intermediary depressions ; one very large 
‘testis : on skin of skates 
Merizocotyle Cerf. (Fig. 17) 
f» Body elongate ; four eyes ; sucking disk elliptical, 
with ten radial ridges ; two testes ; no vagina: 
on gills of Remora .  Dionchus Goto (Fig. 18) 
f$ Body ovoid ; sucking disk circular, with numerous 
radial ridges, with no large, but a group of minute, 
hooks on its edge ; testes numerous: on skin of 
marine fishes. . Lophocotyle Braun (Fig. 19) 
€» Anterior glandular areas inconspicuous. 
Jı Body heart-shaped ; sucking disk with seven radial 
ridges ; testes numerous: on skin and in the 
cloaca of marine fishes 
Calicotyle Dies. (Fig. 20) 
Ja Body elongate; sucking disk with eight radial 
ridges ; three testes : on skin of marine fishes 
Monocotyle Taschbg. (Fig. 21) 
ó,. Body usually elongate and flattened, though sometimes broad, with a 
more or less distinct disk-like region at hinder end, bearing either 
suckers, or hooks, or both ; paired anterior suckers either present 
or absent. 
cı. Posterior disk-like region with suckers, usually paired, and, in 
most cases, with hooks ; anterior paired suckers either present 
or absent. 
d,. Posterior region with either two or six suckers; paired 
anterior suckers absent. . Subfamily I. Polystominz 
e, Posterior region with two (one pair) large suckers and 
two large hooks ; body elongate: on skin of Nec- 
turus . . . . Sphyranura R. R. Wr. (Fig. 22) 
e. Posterior region with six (three pairs) suckers and with 
or without a terminal projection. 
f, Posterior region without a terminal projection ; body 
rather broad ; vagina paired, with an opening on 
either side of body: on gills and in urinary 
bladder of amphibians, and in mouth, nose, and 
urinary bladder of turtles | 
Polystoma Zeder (Fig. 23 
Jy Posterior region with a terminal projection. 
£y Posterior disk-like region bearing the suckers 
is oval, the terminal projection is rather wide 
