156 ILLINOIS BIOLOGICAL MONOGRAPHS [156 



in the size of the eggs. In size P. perplexus somewhat resembles P. 

 singularis. It also resembles P. singularis in the shape and proportions 

 of its proglottids and in the character of the vagina and vaginal sphinc- 

 ter. These two species differ in the size and shape of the head, suckers, 

 and neck. Tho nearly of the same size the strobila of P. perplexus is 

 the larger. P. perplexus has more numerous testes, a larger cirrus- 

 pouch and more numerous coils of ductus ejaculatorius. The main 

 excretory vessels of P. perplexus are straight, but they are very sinuous 

 in P. singularis. P. perplexus differs from all the European species in 

 the position of the sphincter vaginae and in the extension of the vitel- 

 laria along the posterior border of the proglottid. 



PROTEOCEPHALUS SINGULARIS La Rue 



[Figs. 24, 25, 39-41, 83-87] 

 1911 : Proteocephalus singularis La Rue, 1911 :479 



Specific Diagnosis: Characters of the genus. Strobila long and 

 slender. Observed length up to 170 mm., length probably as much as 

 250 mm. in complete individuals. Maximum breadth up to 0.90-1.0 mm. 

 Head small, 0.250-0.30 mm. broad by 0.20-0.22 mm. long. Head bear- 

 ing at broadest part four large suckers. Apical region of head fre- 

 quently prolonged into an unarmed rostellum-like organ. Deep grooves 

 between suckers. Suckers of variable shape, always with pointed apex, 

 with shallow cavity and thin muscular wall. Length of suckers 0.130- 

 0.170 mm., breadth of same 0.170-0.190 mm. No fifth sucker, no vestige 

 of same. Neck slender, 2.0-3.0 mm. long by 0.1-0.2 mm. broad. First 

 proglottids broader than long, 0.255 mm. broad by 0.017-0.020 mm. 

 long. Mature proglottids as much as 0.85 mm. broad by 0.34-0.37 mm. 

 long. Ripe proglottids longer than broad or quadrate 0.680 mm. broad 

 by 0.90-1.00 mm. long. Old spent proglottids up to 2.0 mm. long by 

 0.4 mm. broad. Segmentation evident. Posterior angles of proglottids 

 slightly projecting. 



No genital papilla. Genital pore marginal, irregularly alternating, 

 situated at end of first y±-y 2 of proglottid. Testes numerous, 75-80 or 

 90, in a single layer occupying entire field between vitellaria anterior 

 to ovary. Breadth of testes 0.4-0.6 mm., length of same 0.07-0.10 mm. 

 Vas deferens a large mass of coils in the mid-field. Ductus ejaculato- 

 rius with few or no coils. Cirrus slender, straight, muscular. Cirrus- 

 pouch slender, nearly straight, muscular, 0.185-0.20-0.265 mm. long. 

 Length of cirrus-pouch 2%-3 times into proglottid width. 



