619 



The types of this species should be compared with D. tetra- 

 gona, and T. bothiioplitis, as the worms are very similar, if 

 not identical. The character of the genital as a specific 

 difference I can hardly admit for this form. (See the discus- 

 sion under D. tetragona.) Meg-nin states that the hooks of 

 the middle rows of the suckers are the larg-est and this, if the 

 observation is confirmed, would separate the species from T. 

 bothrioplitis. 



b. Genital pores unilateral, occasionally alternate. 



23. DAVAINEA TETRAGONA (Molin, 1858) R. Blanchard, 1891. 



(1858, Taenia tetragona Molin; 1881, T. bothrioplites Plana 

 (nomen nudum); 1882, T. bothrioplitis Plana.) 



[PI. XVII, figs. 219-227; PI. XVIII, figs. 228-235.1 



Diagnosis: 12mm to 90mm long (Molin) or to 200mm (Plana) or 

 to 250mm (Krabbe), by 1.6mm to 3mm broad. Head small, tetra- 

 gonal; retractile rotellum armed with a double row of about 

 200 hooks, 6 /i long. Suckers circular, armed with seven or 

 eight concentric rows of books of varying size. Neck very 

 long. Anterior segments very short; the following subquad- 

 rangulai', the posterior edges overlapping. Genital pores uni- 

 lateral or irregularly alternate, situated in or about the middle 

 of the imargin. Eggs arranged irregularly in groups of 5-20 

 in egg capsules. 



Development: According to Piana, the larval stage (Mono- 

 cercus Davaineae tetragonae) develops in snails (Helix carth- 

 usianella or H. maculosa). 



Hosts: Chickens. 



Geographical distribution: Italy (by Molin, Piana), Turkestan 

 (by Fedtschenko), Abyssinia (Pasquale), America (Washing- 

 ton, D. C, by Moore). 



Epidemics: Italy by Piana; Washington, D. C, by Moore. 



I include T. botlii*ioplitis in the species D. tetragona 

 and retain D. ecliinobotlirida as a distinct species, 

 chiefly in deference to the opinion of my friends R. 

 Hlanchard and Railliet. Personally I do not see why 

 the species D. tetragona should be recognized, or why 

 two of these forms should be united while the third 

 is kept distinct, for the descriptions of all three forms 



