892 THE AMERICAN NATURALIST. [VoL. XXXVI. 
cĉ» Sucking disk with four rows of depressions; one testis; mar- 
ginal sense organs. 
d. Number of depressions seventy-seven; small protrusile 
tentacle-ike sacks at the corners of the ridges: in the 
stomach of sea turtles . . . .  Lophotaspis Lss. - 
d, Number of depressions 64-120; no protrusile sacs: in 
fresh-water mussels 
Aspidogaster v. Baer (Fig. 7) (58, 66) 
KEY TO THE FAMILIES, SUBFAMILIES, AND GENERA OF THE 
SUBORDER MALACOCOTYLEA. 
x 
e 
. But one sucker present (see p. 908). 
s Two suckers present, the oral sucker and the acetabulum, together with 
a large variously constructed ventral projection or disk of use in 
attachment (see p. ). 
4,. Two suckers present, the oral sucker and the acetabulum, the latter 
either at the posterior end or in the mid-ventral surface; no other 
organ of attachment present. 
6,. Acetabulum at posterior end, either terminal or subterminal 
Family I. Paramphistomide 
c,. Lateral pharyngeal pockets not present; cirrus sac absent 
Subfamily I. Paramphistomine 
4,. Genital pore opens near oral sucker into a large pouch; 
acetabulum terminal; body cylindrical: in herbivores 
Gastrothylax Poir. (Fig. 8) (11) 
4, Genital pouch not present; testes near center of body; 
ovary behind them: usually in herbivores. 
£, Pharynx with ring-shaped projection near its hinder 
end; intestine long and serpentine 
Stephanopharynx Fisch. (11) 
€» Pharynx without ring-shaped projection ; body conical ; 
acetabulum subterminal 
Paramphistomum Fisch. (Fig. 9) (1!) 
c» Lateral pharyngeal pockets present; cirrus sac present 
ubfamily II. Cladorchinz 
d,. Ventral surface with numerous papilla. 
e,- Acetabulum minute and subterminal; body made up of 
two portions, a slender anterior portion and a very 
broad, disklike posterior portion, which contains numer- 
ous papilla on its concave ventral surface : in intestines 
of herbivores ^ Gastrodiscus Leuck. (Fig. 10) (11) 
ey. — large and subterminal; entire ventral sur- 
ace covered with papillae : in intestine of mammals 
Homologaster Poir. (Fig. 11) (11) 
A 
2 


