52 ILLINOIS BIOLOGICAL MONOGRAPHS [52 



Genital aperture marginal, irregularly alternating, situated near 

 middle of proglottid length. Male organs as in genus. Testes spher- 

 ical, 0.031-0.038 mm. in diameter, about 100 in number. Testes packed 

 in area between vitellaria. Coils of vas deferens in middle of proglot- 

 tid. Ductus ejaculatorius nearly straight. Cirrus straight, with a 

 thick wall. Cirrus-pouch ovoidal, broad at inner end, extending to 

 middle of proglottid. Female organs as in genus. Vagina always an- 

 terior to cirrus-pouch. Uterus in ripe proglottids made up of 4-6-8 

 lateral pouches on either side. Diameter of eggs 0,037-0.038 mm. 



Habitat: In intestine and pyloric coeca of Alosa finta var. lacus- 

 tris Fa, (type host) ; Lake Como, Italy (type locality). 



The material was collected by Prof. Ciro Barbieri at Bellagio on 

 Lake Como in Italy from the intestines and pyloric coeca of Alosa fiiita 

 var. lacustris Fa. He found them here in great numbers, up to 1200- 

 1400 in a single host. 



Barbieri (1909) described this species. La Rue (1909:475) in- 

 cluded it in a list of species of Proteocephalus. Since it was impossible 

 to secure specimens for study the present description is based upon Bar- 

 bieri 's description. 



The scolex (Fig. 158) is very small, with a diameter of about 0.168 

 mm. It is unarmed and has no fifth sucker. The four suckers are 

 circular in outline and they are symmetrically arranged on the head. 

 The neck, which is about 3 mm. long and 0.140 mm. broad, is not well 

 differentiated from the strobila. The proglottids are very variable in 

 number and form. One well developed individual with ripe eggs in 

 the last proglottid had 50-70 proglottids. The first proglottids are 

 broader than long. Mature proglottids are longer than broad, 0.580- 

 0.620 mm. long by 0.330-0.370 mm. broad. Ripe proglottids filled with 

 eggs are nearly quadrate, length and breadth being about 0.5 mm. The 

 length of the worm is variable. Well developed individuals measure 

 30 mm. long while a single individual measured 40 mm. 



The genital aperture is marginal, irregularly alternating, situated 

 about the middle of the length of the proglottid, and marked by a 

 shallow depression. The testes (Fig. 185) fill the whole area between 

 the vitellaria anterior to the ovary. They are nearly spherical, 0.031- 

 0.038 mm. in diameter. Barbieri figures about 100 testes. The coils of 

 the vas deferens form a thick mass which occupies the middle region 

 of the proglottid. Its walls are thin and its lumen large. The ductus 

 ejaculatorius has a sinuous course in the inner two-thirds of the cirrus- 

 pouch but apparently it forms no closely twisted coils before it passes 

 over into the straight heavy-walled cirrus. The cirrus-pouch extends 



