619 



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

 gona and T. bothrioplitis, 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. tetrag-ona.) Megnin states that the hooks of 

 the middle rows of the suckers are the largest and this, if the 

 observation is confirmed, would separate tht species from T. 

 bothrioplitis. 



b. Genital pores unilateral, occasionally 



23. DAVAINEA TETRAGONA (Molln. 1858) R. Blanchard. 1891. 



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



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



[PI. XVII, figs. 319-227; PI. XVIII, figs. 228-235.1 



Diagnosis: 12mni to 90mm long (Molin) or to 200nim (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 /* long. Suckers circular, armed with seven or 

 eight concentric rows of hooks of varying size. Neck very 

 long. Anterior segments very short; the following subquad- 

 rangular, the posterior edges overlapping. Genital pores uni- 

 lateral or irregularly alternate, situated in or about the middle 

 of the margin. Eggs arranged Irregularly in groups of 5-20 

 in egg capsules. 



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

 cercus Dayaineae 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. bothrioplitis in the species D. tetragona 

 and retain D. echinobothrida as a distinct species, 

 chiefly in deference to the opinion of inv friends R. 

 Blanchard 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 fomis 



