98 CH. VVARDELL STILES AXD ALBERT HASSALL 



Cirrus pouch ? ; lesticles two ; vitellogene glands profusely 

 developed and extending distal of testicles ; oesophagus 

 short ; body much broader than long. — Type : Distoma 

 squamula Rudo\])hi Eurysoma. 



Cirrus pouch large ; one testicle présent in distal portion of 

 body ; vitellogene glands anterior, and small, as in Bfa- 

 chycœlium ; body longer than broad ; Oesophagus absent. 

 — Type : Distormim monorchis Stossich . . . . Monorchis. 



Subfamily Schistosominae. 



14. Acetabulum semi-pedunculate; intestinal caeca anastomose 

 distal of acetabulum ; testicles more than two ; latéral 

 margin of maie curved ventrally to form gynaecophoric 

 canal for filiform female ; knoAvn only in birds and 

 mammals. — Ty^e : Distoma hœmatohium . . Schistosoma. 

 Acetabulum sessile ; intestinal caeca not anastomosed ; maie 

 filiform ; posterior portion of female swollen to rénal 

 shaped body. — Type : Monostoma fiUcolle . . KœlUkeria. 



A critical study of the above analytical key, and an attempt to 

 détermine published species of Trematodes by means of it, leads 

 us to the conclusion that some of the gênera appear to be well 

 established upon the characters given, and to represent homoge- 

 neous groups. Other gênera cannot be Judged at présent until the 

 type species and closely allied forms are more carefully studied ; 

 still other gênera contain heterogeneous forms, and must be fur- 

 ther divided, oj- better established upon characters which are not 

 yet recognized as of generic value. 



Besides the groups discussed in this i)aper Ihere are a number 

 of gênera proposed by various authors for larval toi-ms. As already 

 stated thèse gênera cannot claim the protection of tiie lexprioritatis, 

 although^they may of course be introduced at any time as generic 

 names for any adult forms should new generic names be required. 

 It is needless to ]emark_that if used at ail in the future as generic 

 names of adults, they should be used in connection with the 

 species with whcse larvae they hâve already been associated. For 

 thèse larval gênera the readeris referred to Diesing, 1855, Révision 

 lier Cercarieen in Sitzb. d. k. Akad. Wien, VI, pp. 377-400. 



I 



