174 



PLATHELMINTHES 



Key to the genera of Tristomidae here described: 

 Oi Sucking disc not set off from body and with 7 radial ridges. . .1. Tristoma 

 02 Sucldng disc set off from body and without radial ridges. 

 6j Body elongate; sucking disc terminal with many minute hooks. 



2. NlTZSCIIIA 



62 Body elliptical ; sucking disc ventral with large hooks 3. Epibdella 



1. Tristoma Cu- 

 vier. Body very flat, 

 circular, or oval, with 

 a pair of anterior suck- 

 ers and a large ventral 

 sucking disc in which 

 are 7 radial ridges and 

 small hooks ; intestine 

 with side branches; 

 genital pores near the 

 margin of the body; 

 many testes present : 

 about 10 species. 



T. coccineum Cuv. 

 (Fig. 279). Body about 

 15 mm. long and 16 

 mm. wide and red in 

 color: on the gills of 

 the swordfish. 



2. NiTZSCHiA von Baer. Body elongate, with sucking disc terminal 

 and without radii; 2 large suckers at forward end; numerous testes: 1 

 species, in salt and fresh water. 



N. sturionis (Abildgaard) (Fig. 280). Body red- 

 dish, 16 mm. long, 5 mm. wide ; sucking disc globose : on 

 gills of the sturgeon. 



3. Epibdella Blainville. Body elliptical and flat; 

 sucking disc ventral without ridges, but often with 

 papillae; 4 small eyes; 2 testes: several species. 



E. bumpusi Linton (Fig. 281). Length 12 mm.; 

 width 8 mm. : on skin of Dasyatis centrura: Woods Hole. 



Family 2. MONOCOTYLIDAE. 



Flat and circular or elliptical worms without paired 

 anterior suckers and with a single posterior sucking plate, 

 which is sometimes vei-y small : on the skin, gills, or in the 

 cloaca of marine fishes; 7 genera. 



MoNOCOTYLE Taschenberg. Sucking disc with 8 

 1 to 3 testes: on the skin or gills of skates. 



Fig. 279 — Tristoma coccineum (from Bronn). 

 References as in Fig. 278. 



Fig. 280 



Nitzschia 



sturionis 



( Monti celli). 



References 



as in Fig. 278. 



radial ridges ; 



