70 ILLINOIS BIOLOGICAL MONOGRAPHS [358 



MARSIPOMETRINAE Cooper 1917 



Scolex with two typical and fairly deep bothria and a terminal disc. Exter- 

 nal segmentation very distinct and regular. Opening of cirrus and vagina 

 marginal, irregularly alternating; uterus-opening surficial, ventral, at the same 

 level with the genital cloaca or very slightly behind it. Only one set of gen- 

 italia in each proglottis. Testes in medulla between the nerve strands. Mus- 

 cular vesicula seminalis outside of the cirrus-sac absent. Receptaculum 

 seminis large, sharply separated from the spermiduct. Ovary not exactly in 

 the median line but slightly approaching the margin bearing the genital cloaca, 

 ventral, as is the shell-gland. Uterus in the form of a sac developed by the en- 

 largement inwardly of that portion of the duct passing thru the cortical paren- 

 chyma. Eggs without opercula. 



Type genus: Marsipometra Cooper. 



As regards the general form of the scolex and the facts that the genital cloaca 

 is marginal and that a vesicula seminalis is absent, Marsipometra comes closest 

 to the Triaenophorinae ; otherwise, however, it is related to other subfamilies. 

 External segmentation is distinct and very regular, a neck being present as in 

 Diphyllobothrium and Bothridium of the Diphyllobothriinae. The uterus- 

 opening is at the same level with the genital cloaca, and not ahead of it as in 

 the Triaenophorinae. Furthermore, as in most of the subfamilies there is 

 only one set of genitaUa in each proglottis. The testes are situated in the medulla 

 between the nerve strands as in the Haplobothriinae. Unlike the structure in 

 the Triaenophorinae, the receptaculum seminis is large and sharply separated 

 from its continuation, the spermiduct, which also obtains for the Liguhnae, 

 Haplobothriinae, Diphyllobothriinae and Cyathocephalus. The ovary is 

 comparable to that of Triaenophorus, Anchistrocephalus and Anonchocephalus 

 (cf. Liihe, 1902:325) in that it is not exactly in the median line but situated 

 towards the margin bearing the genital cloaca. As in the Triaenophorinae, 

 however, the uterus "nie die sogenannte Rosettenform bildend, vor seiner 

 Mundung meist etwas erweitert, ohne dass indessen diese Erw^eiterung ver- 

 haltnissmassig so betrachtlich ist, "wie die sogenannte Uterushohle der meisten 

 Ptychobothriiden. " This latter difference is further emphasized by the fact 

 that at no stage in its development is the beginning of the uterus, which might 

 be considered at first sight to be a true uterine duct, sharply separated from, the 

 enlarged portion as in the Ptychobothriidae. The outstanding feature that 

 the eggs axe nonoperculate has been noted under the remarks on the family. 



MARSIPOMETRA Cooper 1917 



Dibothrium Linton 1897 



Bothriotaenia Ariola 1900 



Scolex unarmed, sagittate. Neck present; strobila flat, ribbon-shaped: 

 proglottides ahnost rectangular, posterior borders only slightly projecting. 



