166 G. A. and W. G. MacCallum, 



in living- in pairs enclosed in cysts, a niode of life which brings with 

 it modifications and retrogressions of various organs. They are distinct 

 from Koellikeria in the form of t.he body which is long and cylin- 

 drical but siniilar in the possession of a long cord-like ovary and 

 vitellarium and in the position of the genital opening at tlie cephalic 

 extremity. I should prefer with Braun to regard Nematobothrium 

 as a part of the family KoeUikeriadae, separate from the Monosto- 

 midae or Distomidae and define the genus as follows: 



Nematohothrium van Beneden, 1858. 



Trematodes of greatly elongated form living in the mature State 

 in pairs in cysts in gills or flesh of sea fish. Digestive tract in 

 various degrees of retrogression. Hermaphrodite but tending to 

 retrogression of one sex in each. Genital openings directly behind 

 mouth at cephalic extremity. Ovary and vitellarium in form of long 

 coiled cords, shell gland and seminal reservoir well developed, uterus 

 forming extremely long coiled tube. Single testis and vas deferens, 

 rudimentary penis, 



The forms recognized up to the present are: 



N. filarina van Beneden Sciaena aquila 



— guernei Moniez Thynnus alalonga 



— molae Maclaeen Orthagoriscus mola 



— taenioides (?) Monticelli „ „ 



— sardae n. sp. Sarda sarda. 



Literature. 



Ariola, in: Arch. Parasitol., Vol. 6, 1902, p, 99. 



Braun, Vermes, in : Bronn's Klass. Ordn. Thier-ßeich. 



— , in: Ctrbl. Bakteriol., Vol. 10, 1891, 424. 



van Beneden, in: CR. Acad. 8c. Paris (suppl.). Vol. 2, 1861, 1 — 376. 



Maclaren, I.D., Jena, 1903. 



Moniez, in: CR. Acad. Sc. Paris, Vol. 111, 1890, 833. 



