ON AVIAN CESTODES. 589 



43. Contributions to the Anatomy and Systematic Arrange- 

 ment of the Cestoidea. By Frank E. Beddard, M.A., 

 D.Sc, F.R.S., F.Z.S., Prosector to the Society. 



[Received October 1, 1915 ; Read October 26, 1915.] 

 (Text-figures 1-6.) 



XVIII. On Taenia strvthioxi.s (Parona) and 

 Allied Forms. 



Index. 



P<i,2;e 



Introductory 5^9 



Description of i>rtyamert sp 590 



I have in my possession a considerable number of examples of 

 a C'estode from the Ostrich Struthio masaicus, which are either 

 identical with Tceuia struthionis of Parona*, or belong to a 

 closely allied species. The description given by Parona is not 

 quite sufficient to enable the identity of his species and mine 

 to be established beyond doubt. But it is at least clear, as I 

 shall point out presently, by comparing the facts of structure 

 one by one, that the species described by Parona and that to be 

 described here by myself are not to be referred to the species 

 described under the same specific name by v. Linstow t. 



Although the details given by Pavona are scanty, tJiey are 

 quite sulficient in my opinion to forbid any confusion between 

 his species and that more fully dealt with by v. Linstow. My 

 chief reasons for_ regarding them as two distinct species are the 

 following. In the first place, v. Linstow's Cestode was obtained 

 from Struthio molyhdophanes ; I infer that Parona obtained his 

 worms from Stridhio camelus. The scolex of Tcenia struthionis 

 of V. Linstow is only 1*18 mm. broad, while the species described 

 by Parona has a stouter scolex of 2 mm. diameter +. 



" Ein eigentliche Rostellum ist nicht vorhanden " — says 

 V. Linstow of his species, while that described by Parona 

 has, according to his figure, a quite strong rostellum. Corre- 

 lated with this would appear to be the feebler character of 

 the rostellar hooks ill the worm from Struthio molyhdophanes. 

 The width of the proglottirls in the two forms also appears to 

 differ greatly ; in the Tfeniid described by v. Linstow, the diameter 

 is but 4 mm. ; while in Parona's specimens the same measure- 

 ment was from 8 to 9 mm., i. e. quite double that of the first- 

 named variety. This seems, like the other feature mentioned in 



* Ann. Mus. Civ. Geneva, (2 a) ii. 1885, p. 425. 



t Arch. Mikv. Anat. xliii. 1893, p. 447. 



X Hut see the observutions of ZiHufT quoted later (on p. 591) which tend to 

 reduce the importance of this apparent difference, but do not affect what f'olh)ws 

 in the above resnme. 



Prog. Zool. Soc— 1915, Xo. XLL 41 



