TREMATODES : CLASSIFICATION 233 



forms that inhabit cysts. Gut with pharynx and a not very long oesophagus and 

 caeca, which end more or less shortly before the hind end. Excretory bladder 

 Y-shaped or tubular. Pars prostatica and seminal vesicle always distinct. Testes 

 elongated, symmetrically placed in or behind the middle of the body. Ovary directly 

 in front of the testes, right-sided, generally much lobed. Receptaculum seminis 

 and Laurer's canal present. Vitellaria generally well developed, exclusively or for 

 the most part confined to the dorsal surface, leaving only a median band unoccupied. 

 Uterus either very long, coiling here and there, or shorter and more convoluted. 

 Eggs in first case small 17 ^ to 25 /*, in the second much larger 63 p. to 85 /* or 

 even 120 /i (?) long. Parasitic in carnivora or birds, generally occurring in pairs 

 in cyst-like cavities. Genera : Paragonimus, Pholeter, Collyriclum, Troglotrema. 



Family. Echinostomidae, Looss, 1902. 



More or less elongated flukes, small or very large, much flattened anteriorly, 

 less so posteriorly, or even round. Suckers near one another, the anterior small and 

 weak, the posterior large and powerful directed obliquely backwards. Surrounding 

 the oral sucker dorsally and laterally but not venlrally is a fold or " collar " bearing 

 a row or rows of pointed spines which are continued round laterally on to the ventral 

 corners, the number being constant for each species, the corner spines large or 

 specialized, skin anteriorly scaled or spiny. Alimentary canal consists of a pharynx, 

 epithelial * pseudo-oesophagus " and gut cceca reaching to posterior end. Testes behind 

 one another in hind body. Ovary on right side or median directly in front of the 

 testes. Vitellaria lateral, usually extending to the hind end and not beyond the 

 ventral sucker anteriorly. Genital pore just in front of ventral sucker. Uterus in 

 transverse loops. Genital sinus absent or present. Receptaculum seminis and 

 Laurer's canal present. Eggs thin shelled and large, bright yellow, 65 ju to 1 20 /* long. 

 Excretory bladder Y-shaped. Parasitic in gut of vertebrates, especially birds. 



Sub-family. Echinostominae, Looss, 1899. 



Cirrus sac usually reaching to centre of ventral sucker, but not beyond. Cirrus 

 long, usually without spines, coiled when retracted. Seminal vesicle tubular, twisted. 

 On the head a ventral uniting ridge between the angles of the collar. Dorsal circlet 

 of spines, single or double, not interrupted unless the collar itself is dorsally divided. 

 Genera : Echinostoma, etc. 



Sub-family. Himasthlinae, Odhner, 1910. 



Cirrus sac reaching far beyond ventral sucker. Cirrus armed with strong 

 rose-thorn-shaped hooks. Vesicula seminalis tubular not coiled. Cervical collar 

 not continued across ventral aspect. Spines on collar in one row. Body armed 

 with fine needle-shaped spines. 



Family. Schistosomidee, Looss, 1899. 



Sexes separate. Genital pore behind the ventral sucker. Ventral sucker 

 elevated above the surface. Pharynx absent. Gut forks reunite to form a single 

 stem. In $ four or more testicular follicles. In <j> a single ovary, just in front 

 of the union of the gut forks. Vitellaria on either side of the united gut stem. 



