MO. 2258 TAENIOID CE8T0DES OF DOGS AND CATS— HALL. 7 



KEY TO THE SPECIES OF TAENIA. 



1. Rostellum with a single circlet of hooks of rose-thorn shape. 



Taenia mono Stephanos, p. 38. 



Rostellum with a douhle crown of hooks of conventional shape, i. e., with 



a relatively long handle 2. 



2. Large hooks 60 to 74 in number ; 320 to 355 fi long ; the large hooks arranged 



alternately nearer to the center of the rostellum and farther from it, 



forming, in effect, 2 circlets of large hooks Taenia macrocystis, p. 13, 



Large hooks not over 60 in number 3. 



3. No neck. Large hooks 380 to 420 m long; hooks 26 to 52 in number, well- 



developed sphincter vaginae Taenia taeniaefonnis, p. 9. 



Neck present, or if absent, large hooks 38 to 60 in number, no sphincter 

 vaginae 4. 



4. No neck. Large hooks 38 to GO in number ; 380 to 420 fi long. 



Taenia laticollis, p. 8. 

 Neck present. Large hooks not over 294 fi long , 5. 



5. Large hooks 225 to 294 fi long. Small hooks deeply bifid. Testes extend 



posterior of the vitellarium. Vas deferens originates in a vesicula semi- 



nalis Taenia pisiformis, p. 22. 



Large hooks not over 220 ix long 6. 



6. Guard of small hook twisted so that its flat surface tends to lie in the plane 



of the blade and handle Taenia brachysoma, p. 21, 



Guard of small hook not so twisted 7. 



7. Head acorn-shaped with hooks far anterior of the suckers. Mature seg- 



ments approximately square Taenia Mlaniceps, p. 16. 



Head not acorn-shaped and hooks not far anterior of the suckers. Mature 

 segments distinctly broader than long 8. 



8. Large hooks 95 to 140 ii long Taenia brauni, p. 19. 



Large hooks 148 n long or more (species of Multiccps will run down to here 



with a range of 135 to 180 p.) , 9. 



9. Gravid uterus with 20 to 25 lateral branches on each side of the median 



stem. Vagina crosses the ovary on the pore side in some segments. 



Taenia ovis, p. 32. 



Gravid uterus with not over 10 lateral branches on each side. Vagina does 



not cross the ovary on the pore side of segments 10. 



10. Large hooks 148 to 170 fi long. Genital papilla very large and prominent, 



practically as long as the margin of the segments. Vagina does not form 

 a crescent near segment margin. Gravid segments without a median 

 longitudinal groove terminating in a posterior notch. 



Taenia krahhei, p. 36. 



Large hooks 170 to 220 m long. Genital papilla small and not prominent. 



Vagina forms a sort of crescent by dilation and curvature near lateral 



margin of segment. Gravid segments with a median longitudinal groove 



terminating in a notch posteriorly Taenia hydatigena, p. 28. 



In the above key the distinction between Taenia taeni-aeformis 

 and Taenia laticollis is not well drawn. As a matter of fact, it ap- 

 pears impossible to draw any adequate distinction. All the described 

 specim.ens of T. laticollis appear to have been based on immature 

 specimens, and the descriptions of the genitalia with their topogra- 

 phy, so essential in present-day specific concepts, have never been 

 published. It is an open question in the writer's mind whether there 



