204 ILLINOIS BIOLOGICAL MONOGRAPHS [204 



OPHIOTAENIA PERSPICUA La Eue 

 [Figs. 10, 102] 



1911 : Ophiotaenia perspicua La Rue 1911 :480 



Specific Diagnosis: Characters of the genus. Length up to 36.0 

 cm. Maximum breadth about 2.0 mm. Head conical, flattened, divided 

 by grooves into four quadrants. Breadth of head 0.355-0.408 ,nm., 

 thickness of head as much as 0.306 mm., length about 0.270 mm. Suck- 

 ers four, circular, oval or at times somewhat triangular, 0.105-0.170 mm. 

 in maximum dimension. Cavity of sucker 0.053-0.106 mm. in diameter. 

 Neck long, 5-7 mm. in length by 0.170-0.425 mm. broad. First proglot- 

 tids short. Mature proglottids quadrate, 2.0 mm. in length and breadth, 

 or somewhat longer than broad. Ripe proglottids measure as much as 

 3.8 mm. long by 1.2 mm. broad. Segmentation indistinct. Proglottids 

 attached by full width. Surface smooth. In life and when preserved 

 in formol specimens somewhat translucent. 



Genital pore marginal, irregularly alternating, situated near middle 

 or at end of first third of proglottid. Vagina anterior or posterior to 

 cirrus-pouch. Testes 150-215, oval or polygonal, measuring up to 0.053- 

 0.106 mm., situated in two fields. Vas deferens in ripe proglottids a 

 heavy mass of coils reaching from end of cirrus-pouch to the mid-field. 

 Cirrus-pouch 0.255-0.320 mm. long by 0.080-0.090 mm. broad. Ratio of 

 length of cirrus-pouch to proglottid breadth 1 :4 to 1 :3. Cirrus slender, 

 about 0.20 mm. long when protruded. Vagina dilated in first part, not 

 crossing cirrus-pouch. Sphincter vaginae and receptaculum seminis 

 present. Lobes of ovary long, flattened, irregular in outline, made up 

 of anastomosing tubules. Oocapt and ootype present. Vitellaria loose. 

 Uterus when ripe with 20-30 lateral pouches on either side. Uterine 

 pores not seen. Eggs provided with three membranes, outer one 0.045- 

 0.100 mm. in diameter. Embryos 0.018-0.021 mm. 



Habitat: Natrix (Nerodia) rhombifer Hallowell, (type host) ; 

 Havana, Illinois, (type locality). 



Type : Unaccessioned bottles in coll. La Rue, also bottle in Dr. H. 

 B. Ward's collection. Slides of same. 



The host, a very large female, was caught on the banks of the Illi- 

 nois river at Havana, Illinois, and was examined for parasites July 9, 

 1910. From the intestine 57 cestodes and pieces were taken. Of these 

 42 pieces had heads attached. No strobilas were found with an end- 

 proglottid. There were, however, a number of specimens with ripe pro- 

 glottids. Because of their translucent appearance in life and when pre- 



