T^NIOID CESTODES OF NORTH AMERICAN BIRDS. 53 



embryo, oncosphere) with one or several membranes; without oper- 

 culum. Larval stage in vertebrates or invertebrates. Adults in ali- 

 mentary canal of vertebrates. 



Type-family. — Tseniidse Ludwig, 1886. 



KEY TO GENERA." 



1. Genital pores marginal or (?) absent 2. 



Genital pores ventral, in or near median line; scolex unarmed, without 



rostellum ; a single egg capsule in the gravid segment. 



Mesocestoididte, Mesocestoides, p. 61. 



2. One cirrus pouch in each segment, or two in each segment, one on either 



side 3. 



Several cirrus pouches in each lateral half of each segment ; segmentation 

 not apparent externally ; one testicle, ovary, yolk gland, and uterus in 

 each lateral half of the segment ; egg with well-developed pyriform appa- 

 ratus ; head unarmed, without rostellum ; adults in marsupials. 



Triplotcenia, p. 62. 



3. Vaginal pore anterior of male opening Tetracisdicotyla, p. 106. 



Vaginal pore posterior, dorsal, or ventral of male opening, or absent 4. 



4. Anterior portion of strobila enlarged and modified to form a large pseudo 



scolex ; strobila grooved transversely, but without progilottids. 



Fimbriariidse, FimJjriaria, p. 105. 



Strobila without pseudo scolex; with more or less definite proglottids, or 



segments 5. 



5. Yolk gland in front of ovary; suckers with auricular appendages on an- 



terior border Tetrabothriid^e, Tetrabothrius, p. 59. 



Yolk gland posterior, dorsal, ventral, or lateral of ovary ; suckers without 

 auricular appendages 6. 



6. Vaginal pore lacking 7. 



Vaginal pore present 15. 



7. Male and female genital openings both (?) lacking; scolex without ros- 



tellum ; suckers unarmed ; a single set of reproductive organs in each 

 segment ; female glands near one side of the segment ; cirrus pouch 

 rudimentary, unites with distal end of vagina in lateral field of seg- 

 ment Aporina, p. 64. 



Male genital opening present 8. 



8. Scolex with armed rostellum ; segments with lateral appendages ; accessory 



female genital canal present, functioning as vagina, with dorsal, ventral, 



or marginal opening 9 (Amabiliidse). 



Scolex with or without rostellum ; segments without lateral appendages ; 

 vagina, without external opening, functions as seminal receptacle. 



11 (Acoleidge). 



9. A double set of male reproductive organs and a single set of female organs 



in each segment; two male genital pores in each segment, one on each side; 



opening of accessory vagina ventral AmaMlia, p. 103. 



A single set of reproductive organs in each segment ; male genital pores 



regularly or irregularly alternate 10. 



10. Suckers and posterior portion of head covered with minute spines ; segments 

 of strobila not numerous ; testicles few ; vagina of each segment turns 

 backward into and communicates with the seminal vesicle of the next 



"The genus Copesoma (p. 106) is not included in this key. 



