NO. 2258. TAENIOID CESTODES OF DOOS AND CATS—HALL. 63 



3. Head with 13 or 14 circlets of hooks; strobila 12 to 20 cm. long; 45 to 50 



small testes; cirrus pouch 250 to 260 n long and crossing the longitudinal 

 excretory canals; vitellarium roughly splierical and smaller than the 

 ovarian lobes; 1 large egg, 52 to 53 ft in diameter, in each egg capsule. 



Dipylidiuin chyzcH, p. G8. 



Head with not over 6 rows of hooks; 90 or more testes; 2 or more eggs in 



each capsule 4. 



4. Heads with 6 circlets of hooks; strobila 10 to 23.5 cm. long; 130 to 140 testes; 



cirrus pouch extends to the longitudinal excretory canals ; the median 

 ovarian lobes crescentic. the lateral spherical ; the vitellarium reniform 

 and as large as an ovarian lobe; egg capsules with 2 to 15 eggs and at 

 times extending lateral of the longitudinal excretory canals. 



Dipylidium scxcoronatum, p. 65. 

 Heads with 3 to 5 circlets of hooks; cirrus pouch extends across the excre- 

 tory canals regularly or occasionally ; vitellarium smaller than the ovarian 

 lobes or smaller than the median lobes 5. 



5. Head with 5 circlets of hooks; strobila 5 to 11 cm. long; 90 to 100 large testes; 



cirrus pouch curved, convex posteriorly and extending distinctly across 

 the longitudinal excretory canals; vitellarium smaller than the ovarian 

 lobes ; spindle-shaped receptaculum seminis present ; vaguia opens posterior 

 of the cirrus pouch aperture ; eggs 25 ^ in diameter. 



Dipylidium ocrleyi, p. 63, 

 Head with 3 to 4 circlets of hooks; strobila 15 to 40 cm. long; 100 to 200 

 testes; cirrus pouch piriform and extending to, or occasionally across, the 

 longitudinal excretory canals ; no receptaculum seminis present, the oviduct 

 showing a compensatory dilation ; vagina opens ventral of the cirrus 

 pouch aperture ; eggs 43 to 50 ii in diameter Dipylidium caninum, p. 73. 



Parts of the above key are based on illustrations where the features 

 m question are not specifically covered in the text, and therefore 

 depend for their reliability on the accuracy of the illustrations and 

 the constancy of the features covered. 



DIPYLIDIUM OERLEYI von Ratz. 1900o. 



Specific diagnosis. — Dipylidium: The head (fig. 61) is broad and 

 club-shaped, and is 330 [jl long and 390 fx wide; it tapers anteriorly 

 to form a blunted cone ; it is provided with a rostellum 67 /* long and 

 71 [A wide at the base, conical in shape, with a rounded apex, con- 

 stantly retracted and lying in a deep depression. The rostellum bears 

 5 alternating circlets of hooks covering the lower portion of the cone, 

 the tip of the cone being free from hooks ; the hooks are of rose-thorn 

 shape, with a somewhat bent ventral root and with a bevel-edged 

 funnel-shaped base, so that the entire hook has the general form of 

 a bent funnel. The rostellum is prolonged posteriorly to form a thick 

 muscular mass, with a neck-like constriction anteriorly and termi- 

 nating posteriorly in a large thick conical mass. The 4 suckers are 

 oval and but slightly prominent. The neck is short and thick and 

 diminishes in diameter posteriorly. The entire strobila is 5 to 11 cm. 

 long and consists of 70 to 90 segments. The anterior segments are 



