CESTODARIA 461 



to the exterior, that the arrangement of the genitaha is very 

 distinctive, and that the larva of some species is hexacanth. 

 Taking these features into account, the C a r y o p h y 1 1 a e i d a e 

 may be defined as 



Cestodaria, usually with a slightly flattened cylindrical 

 elongated body but sometimes fluke-shaped, devoid of 

 calcareous corpuscles and cuticular spinelets or hooks, 

 with an anterior end extremely variable in form and size, 

 both in the individual and in different species, which never 

 carries circular suckers but may bear shallow elongated 

 grooves (different in number, form, and arrangement to 

 those found on the scolex of other Cestoda), with the cirrus 

 and vagino -uterine apertures contiguous or nearly con- 

 tiguous on the ventral surface of the body in the median 

 line and occasionally opening into a common shallow 

 atrium, with the testes situated anteriorly and entirely 

 in front of the uterus, with the vagina and uterus forming 

 a complete circuit with a common vagino-uterine opening 

 to the exterior, with a network of excretory channels, the 

 larger ones of which form irregular longitudinal canals 

 about eight or ten in number and all of which open 

 externally by a median posterior excretory bladder, and 

 with a larval form known in some cases to be hexacanth. 

 Parasitic in the intestine of Teleostome fishes (Malaco- 

 pterygii and Ostariophysi) and in the body-cavity of 

 aquatic Oligochaeta (Tubificidae). 



Ee-definition of the Caryophyllaeidae necessitates 

 re-definitions of the other two families of the Cestodaria. The 

 Gyrocotylidae, comprising four species of the well-known 

 genus Gyrocotyle (24, 8, 26), may be defined as 



Cestodaria with a flattened elongated body, devoid of 

 calcareous corpuscles but possessing cuticular spinelets, 

 with an anterior ovoid sucker and a posterior ' rosette ' 

 in all known forms, with the cirrus and vaginal apertures 

 adjacent but not contiguous, and situated anteriorly on 

 the left margin of the body, with the testes situated 

 anteriorly and to the outer sides of the median uterus, 

 with the uterine aperture situated anteriorly on the ventral 

 surface in or near the median line, a short distance but quite 

 separate from the vaginal aperture, with a close network 

 of fine excretory vessels devoid of main longitudinal 



