TAPEWORM PROM APTERYX. 89 



characters, point to its affinities with the other avian Cestodes. 

 The rostellum, which, though constructed on the same plan, 

 is smaller than that of D. minuta (compare figs. 15 and 16, 

 which are magnified to the same extent), is armed with twelve 

 hooks, arranged in a single circle (fig. 10). Each hook is 

 0'03 mm. loug, and is thus smaller than in the preceding 

 worm. The shape, too, is quite different, as the guard and 

 the handle are much smaller, the latter rather larger than 

 the former; it is, in fact, a typical Drepanidotaenian hook 

 (fig. 11). 



The scolex is more nearly square in section than in D. 

 minuta; the suckers have the usual structure found in 

 Tgenia (fig. 12). 



This species is much more like a typical Drepanido- 

 tsenia, except for the shape of the suckers (?), and agrees 

 with one species (not named by Shipley, but referred to) in 

 the alternate position of the genital pores. 



It may be characterised thus : 



Drepanidotsenia apterygis, n. sp. 



A Tetracotylean Cestode, measuring about 100 mm., with 

 some 300 proglottids, much broader at the free end than at 

 the scolex ; the hindmost proglottids are as long as they are 

 broad. The scolex, square in section, has oval suckers, with 

 posterior margin prominent; the rostellum is armed with 

 twelve booklets in a single circle. Each booklet is 0'03 mm. 

 long ; the guard is about equal to the handle, but both are 

 short. The genital pores alternate ; the eggs measure 

 0'03 mm. across the internal shell. Hab., intestine of 

 Apteryx Bulleri, 



The Rostellum of Drepanidotsenia. 



The small size of D. minuta renders it a convenient 

 object for the study of the rostellar apparatus — its structure 

 and the mechanism of its movement — in specimens mounted 

 entire. From the following account it will be seen that it 



