54 BULLETIN 69, UNITED STATES NATIONAL MUSEUM. 



following segment ; an accessory vagina in the opposite side of the segment 



from the cirrus pouch, sometimes with marginal opening Tatria, p. 104. 



Eostellum very large ; suckers and posterior portion of head without spiny 

 armature; testicles numerous, extend across entire width of segment; 

 vagina absent; accessory vagina dorso-ventral, with median opening on 

 dorsal and ventral surfaces of segment HchistoUenia, p. 104 



11. Dicecius, entire strobila male or female ; male with a double set, female with 



a single set of reproductive organs in each segment Dioicocestus, p. 103. 



Moncecius 12. 



12. A single set of reproductive organs in each segments 13. 



A double set of male reproductive organs and a single set of female repro- 

 ductive organs in each segment, with two vaginae functioning as large 

 seminal receptacles Diplophallus, p. 102. 



13. Scolex with armed rostellum 14. 



Scolex without rostellum, but with apical papilla ; cirrus conical in shape, 



armed with large hooks »S7//y)?r//(/, p. 103. 



.14. Rostellum armed with a single crown of hooks arranged in a zigzag row 

 having right angles ; testicles few ; seminal receptacle very small ; uterus 



with dorsal and ventral openings Gyroccelia, p. 102. 



Testicles numerous ; seminal receptacle very large ; uterus without opening 

 to the exterior Acoleus, p. 102. 



15. Scolex with rostellum armed with a double row (rarely a single or triple 



row) of very numerous (and generally very small) hammer-shaped hooks, 

 i. e., with long ventral root, very short dorsal root, and short blade ; 



suckers usually armed 16 (Davaineidfe). 



Scolex with rostellum armed with hooks not hammer shaped, without ros- 

 tellum, or with rudimentary unarmed rostellum ; suckers usually armed- 21. 



16. Rostellum broader than rest of scolex ; suckers armed only near a.nterior 



border ; a single set of reproductive organs in each segment ; uterus sac- 

 like, persistent : Ophryocotyle, p. 67. 



Rostellum not broader than rest of scolex ; suckers armed with several 

 rings of booklets around the periphery or unarmed ; a single or double 

 set of reproductive organs in each segment ; uterus not persistent, re- 

 placed by egg capsules, with or without the formation of para-uterine 

 organs . 17. 



17. Uterus breaks down into numerous egg capsules, each containing one or 



more eggs; para-uterine organs not present IS. 



A para-uterine organ present, into which the eggs pass, and which trans- 

 forms into an egg capsule 20. 



18. A single set of reproductive organs in each segment- 19. 



A double set of reproductive organs in each segment; eggs become inclosed 



singly in egg capsules Cotngnia, p. 69 



19. Rostellum armed with a double or single row of hooks; dorsal excretory 



vessels present; genital pores unilateral or irregularly alternate; egg 



capsules contain one or several eggs Davainea, p. 67. 



Rostellum armed with three rows of hooks; dorsal excretory vessels 

 absent ; genital pores unilateral ; female glands on pore side of median 

 line, near the ventral excretory vessel : eggs become inclosed singly in 

 egg capsules '. Porogynia, p. 69. 



20. Eggs pass directly from uterus into a para-uterine organ, which trans- 



forms into an egg capsule . Idiogenes, p.. 70. 



Eggs become inclosed in numerous egg capsules following the disappear- 

 ance of the uterus, and finally are pressed into a large anteriorly located 

 para-uterine organ which transforms into an egg capsMle-Chapmania, p. 70. 



