646 THE AMERICAN NATURALIST.  [Vor. XXXIV. 
of which exactly coincides with the Monogenea of van Beneden, 
while the second and third are included in the Digenea. This 
arrangement has been generally adopted by recent authors, and 
this synopsis is based upon it. 
The following are the families, subfamilies, and genera of 
the suborder Heterocotylea in Monticelli's system of classifi- 
cation, with certain modifications, however, which have been 
proposed since 1892 by himself, Braun, Cerfontaine, Goto, 
Saint-Remy, and others : 
Order. — Trematoda Rud. 
Suborder I. Heterocotylea Mont. 
Family I. Temnocephalide Hasw. 
Subfamily I. Temnocephaline Mont. 
Genera: Temnocephala, Craspedella, Dactylocephala. 
Subfamily II. Actinodactynellinze Mont. 
Genus : Actinodactylella. 
Family II. Tristomide Taschbg. 
Subfamily I. Tristominz Mont. 
Genera: Tristoma, Nitzschia, Epibdella, Phyllonella, Trochopus, Acantho- 
cotyle, Placunella. 
Subfamily II. Encotyllabine Mont. 
Genus: Encotyllabe. 
Subfamily III. Udonelline Mont. 
Genera: Udonella, Echinella, Pteronella. 
Family III. Monocotylidz Taschbg. 
Genera: Monocotyle, Calicotyle, Lophocotyle, Dionchus, Merizocotyle, 
Microbothrium, Pseudocotyle 
Family IV. Polystomidz Taschbg. 
Subfamily I. Polystominz v. Ben. 
Genera: Polystoma, Erpocotyle, Onchocotyle, Diplobothrium, Sphyranura. 
Kip II. Octocotylinz v. Ben. et Hesse. 
Genera : Octocotyle, Octobothrium, Dactylocotyle, Diclidophora, Antho- 
cotyle, Vallisia, Diplozoðn Phyllocotyle, Hexacotyle, Plectanocotyle, 
Platycotyle, Pleurocotyle. 
aum III. Microcotylinz Taschbg. 
Genera: Microcotyle, Gastrocotyle, Axine, Pseudaxine. 
Family V. Gyrodactylidz v. Ben. et Hesse. 
Genera: Gyrodactylus, Dactylogyrus, Tetraonchus, Diplectanum, Calceo- 
stoma, Amphibdella, Dactylodiscus, Fridericianella, Anoplodiscus. 
