74 BULLETIN 09; UNITED STATES NATIONAL MUSEUM. 



Genus CHOANOTv^NIA" Railliet, 1896. 



Monopylidium Fuhrmann, 1899 (type, Davainea musculosa Fuhrmann, 1896; 



in part). 

 Icterotsenia Railliet and Henry, 1909 (in part). 



Generic diagnosis. — Dipylidiinae : Rostellum armed with a single 

 crown of hooks usually with long dorsal and short ventral root. 

 Segments numerous, rarely less than 30. Genital pores irregularly 

 alternate near the anterior border of the segment. Genital canals 

 pass between the longitudinal excretory vessels and dorsal of the 

 nerve. Vas deferens coiled, seminal vesicle absent. Testicles numer- 

 ous, in the posterior region of the segment, or, also, laterally on each 

 side of the female glands. Uterus persistent, sac-like, but may be 

 subdivided into numerous small communicating chambers incom- 

 pletely separated by partitions infolded from the wall of the uterus, 

 so that in some cases the eggs appear almost as if isolated in the 

 parenchyma. Adults in birds and mammals. 



^Although Fuhrmann (1908a, 1907a) and Clerc (1903) recognize Monopylidium and 

 Choanotaenia as distinct genera, they would place Ch. infundibuliformis, the type of 

 Choanotsenia in Monopylidium, and Fuhrmann (1908a) has selected Choanotxnia 

 galhulx (Zeder, 1803) as a new type for Choanotxnia. This arrangement, as has been 

 pointed out by Railliet and Henry (1909, p. 338), is in violation of the law of priority 

 of the Intei'national Code of Zoological Nomenclature, inasmuch as a type once fixed 

 can not be changed. Monopylidiuin must fall into synonymy if Ch. infundibuliformis 

 (type of Choanotsenia) is made congeneric with Monopylidium musculosum (type of 

 Monopylidium), Choanotsenia (1893) being of date prior to that of Monopylidium (1899). 

 If, as Clerc and Fuhrmann believe, Ch. infundibuliformis and M. musculosum should 

 go into the same genus, that genus must be known as Choanotsenia, not as Monopyli- 

 dium. Such action would leave the genus Choanotsenia of Fuhrmann (not Railliet) 

 without a name, and it would become necessary to rename the genus. This Railliet 

 and Henry (1909, p. 338) have done, proposing the name Icterotsenia for the species 

 ^ ^ Icterotsenia galbulse , porosa, parina, etc." Until, however, a more careful compara- 

 tive study of the various species of Monopylidium, and Choanotsenia, especially the 

 type species of the two genera, has been made I believe it justifiable to recognize 

 both these generic names, notwithstanding this necessitates the separation of Choano- 

 tsenia infundibuliformis and Monopylidium musculosum, which Clerc and Fuhrmann 

 would place together. I am inclined to doubt that the uterus of the former species 

 breaks down into egg capsules as Clerc (1903) has stated. My own observations 

 support those of Cohn (1901b), who affirms that the uterus is persistent, and pos- 

 sesses an irregularly lobulated cavity incompletely subdivided by infoldings from the 

 wall. If this is true, and if no later development of egg capsules occurs, Choanotsenia 

 infundibuliformis differs from Monopylidium, in which the uterus is said to break 

 down into egg capsules, and it is therefore possible to recognize both Choanotsenia 

 and Monopylidium changing but slightly Fuhrmann's arrangement of species, namely 

 removing Choanotsenia infundibuliformis from Monopylidium to Choanotsenia, where 

 it belongs. I have not considered the differences between Monopylidium and such 

 genera as Choanotsenia, and Anomotsenia, sufficiently marked to warrant placing them 

 in different subfamilies, as Fuhrmann (1907a, 1908a) has done. Monopylidium, in spite 

 of the breaking down of the uterus, seems to me much more closely related to the 

 genera named than to Dipylidium, with which Fuhrmann has united it in a sub- 

 family separate from the others. 



