42 ILLINOIS BIOLOGICAL MONOGRAPHS [392 



known S. decrescens should not be given serious consideration. Its 

 position in the genus is not assured and the statements concerning it are 

 not clear-cut and dependable. The conception of the genus must be 

 changed in the following particulars: 



1. The testes do not necessarily extend "von Langsgefass zu 

 Langsgefass" in the distal part of the proglottid. They may be in two 

 lateral groups, or all on the pore side, and they may be mostly anterior. 



2. In the main the genital canals "ziehen dorsal an den beiden 

 Excretionsgefassen und dem Nervenstrang vorbei"; yet recognition 

 must be given to the fact that the opposite may be the case in some 

 proglottids. 



3. The position of the vagina and vaginal pore anterior to the 

 cirrus pouch is an absolute distinction from all other known genera of 

 the subfamily and indeed from nearly all known cestodes, and should 

 have recognition as perhaps the most important generic character. The 

 unsatisfactory description of S. decrescens is noncommittal but gives 

 no information opposed to the conclusion that the vagina is anterior 

 here also. 



4. The union of the oviduct with the ovary in all sufficiently 

 known species of the genus is located directly anterior to the middle 

 of the vitelline gland. This fact should be stated in the diagnosis. 



5. The diagnosis should state that cirrus is spiny. 



Accordingly the genus Schizotaenia should be characterized as 

 follows : 



Anoplocephalinae, with segments broader than long. Genital pores 

 regularly alternate or dextral, and in one doubtful species irregularly 

 alternate. Dorsal excretory duct lateral of ventral. Genital canals 

 pass usually dorsal of longitudinal excretory vessels and nerve, tho the 

 reverse condition has been observed. Testes confined to the median 

 field, either distal in position or proximal, and mostly on the pore side. 

 Cirrus pouch very large and muscular, cirrus spiny. External vesicula 

 seminal is present. Vagina and vaginal pore anterior to the cirrus 

 pouch. Female glands placed towards the pore side of the median 

 field. Oviduct joins the ovary directly in front of the middle of the 

 vitelline gland. Uterus not a simple transverse tube, usually perhaps 

 always a degenerate reticulum; confined to the median field in anlage, 

 and in its fully developed stage either there or crossing the excretory 

 ducts mostly on the dorsal side. No pyriform apparatus. Adults in 

 mammals. 



Designated as type : Schizotaenia decrescens Diesing 1856. 



