72 ILLINOIS BIOLOGICAL MONOGRAPHS [352 



condition of the acetabulum suggested the name Zygocotyle as appropriate 

 for this genus. Zygocotyle ceratosa has been designated as type and in 

 the genus is included also the species Amplvistoma lit nation. 



As diagnostic characters of the genus Zygocotyle may be mentioned 

 the subterminal oral sucker, the posterior sucker divided or provided 

 with caudal overhanging lip, absence of cirrus sac and separate openings 

 of the male and female ducts. Others will undoubtedly appear when 

 the character of the excretory and lymph systems are known. The genus 

 Zygocotyle differs from all other known genera of the Paramphistomidae 

 in the ventral position of the oral sucker and the peculiar character of 

 the acetabulum. It differs from the Gastrodiscinae in the shape of body 

 and absence of ventral papillae, and from the Gastrothylacinae in the ab- 

 sence of the ventral pouch. In the lobed testes and absence of cirrus 

 sac it agrees with the Paramphistominae, but the oral evaginations ex- 

 clude it from that group. The absence of cirrus sac and the lobed form 

 of the testes will not permit its inclusion with the Cladorchinae. The 

 characters of the Diplodiscinae are so poorly defined that a comparison 

 is unsatisfactory ; in this group however, a cirrus sac is present and both 

 suckers are terminal. As none of the existing subfamilies will include 

 the genus, a new subfamily will probably have to be made to contain it. 

 Since the present classification of the Paramphistomidae is somewhat un- 

 certain, and the structure of the excretory and lymph systems of this 

 genus are as yet unknown, no further attempt at classification of the 

 group is made at this time. 



ZYGOCOTYLE CERATOSA Stunkard 1916 



[Figures 72 to 79] 



The material of this species consists of eight specimens from the in- 

 testine of Anas platyrhynchos from Rock County, Nebraska. The intes- 

 tine of the duck had been cut open in places and together with its con- 

 sents preserved in formalin. The fixation of the parasites is so poor 

 ( that the excretory and lymph system can not be traced, altho remnants 

 of both appear in sections. 



These worms (Fig. 72) vary in length from 3 to 6 mm. and in width 

 from 1.45 to 2.14 mm. In dorsal or ventral aspect they are elongate oval 

 jn shape with the acetabulum forming a small terminal projection. The 

 cross section is a flattened oval and toward the ends of the body becomes 

 more circular. The acetabulum is subterminal and consists of two parts 

 (Fig. 77), an anterior part extending dorsally and anteriorly into the 

 body and a posterior overhanging lip which terminates on either side 

 ^n a little horn or conical projection 0.12 to 0.2 mm. in length. The 



