36 ILLINOIS BIOLOGICAL MONOGRAPHS [36 



41(40) Uterine pouches 3 (or 4) on either side; cestodes large and 



robust Proteocephalus longicollis (Zeder 1800) 



42(27) Testes number more than 70 43 



43(44) Fifth sucker armed with minute hooks or spines. 



Proteocephalus osculatus (Goeze 1782) 



44 ( 43 ) Fifth sucker unarmed _ 45 



45(46) Vagina anterior to cirrus-pouch; genital pore posterior to 

 middle of proglottid; suckers 0.25 mm. in diameter. 



Proteocephalus skorikowi (von Linstow 1904) 

 46(45) Vagina posterior to cirrus-pouch; genital pore about middle 

 of proglottid; suckers 0.5 mm. in diameter. 



Proteocephalus pentastoma (Klaptocz 1906) 

 47 ( 2) Testes lie in two lateral fields between vitellaria; parasitic 



in amphibians, aquatic snakes and lizards _ 48 



48(49) Cuticula of head or of head and parts of strobila covered 

 with minute spines. 



Genus Acanthotacnia von Linstow 1903 



49(48) Cuticula of neck free from spines or hooks 50 



50(69) Suckers rounded or oval in outline. 



Genus Ophiotaenia La Rue 1911 

 51(52) Vagina always anterior to cirrus-pouch. 



Ophiotaenia filar oides La Rue 1909 



52(51) Vagina either anterior or posterior to the cirrus-pouch 53 



53 ( 62 ) Genital pore anterior to the middle of margin of proglottid... 54 



54(57) Uterine pouches 20 or less than 20 on either side 55 



55(56) Head 0.24-0.25 mm. broad; suckers 0.12-0.15 mm. in diame- 

 ter ; testes number 80-100 ; cirrus-pouch extends about 

 Y across the breadth of proglottid. 



Ophiotaenia natter eri (Parona 1901) 

 56(55) Head 0.54 mm. broad; suckers 0.27-0.3 mm. in diameter; 

 testes number 100-120 ; cirrus-pouch extends about Y* 

 across the breadth of proglottid. 



Ophiotaenia racemosa (Rudolphi 1819) 



57(54) More than 20 uterine pouches on either side 58 



58(61) Testes number about 100-150 59 



59(60) Testes number 100-108, situated in two narrow lateral fields 

 not near vitellaria ; several coils of ductus ejaculatorius 

 in base of protruded cirrus. 



Ophiotaenia trimeresuri (Parona 1898) 

 60(61) Testes number 90-160, situated in two broad lateral fields 

 extending close to vitellaria, no coils of ductus ejacula- 

 torius in base of protruded cirrus. 



Ophiotaenia lonnhergii (Fuhrmann 1895) 



