10 BULLETIN 69, UNITED STATES NATIONAL MUSEUM. 



with portions from various regions of the strobila chosen to show the 

 male and female organs in different stages of development. Trans- 

 verse and frontal sections are the most useful; occasionally sagittal 

 sections are valuable. Except for fine histological details, thick 

 sections are more satisfactory than thin ones. 



DESCRIPTION OF SPECIES. 

 Genus DAVAINEA Blanehard and Railliet, 1891. 



(For generic diagnosis see p. 67.) 



DAVAINEA RHYNCHOTA, new species. 

 Figs. 1-i. 



This species is represented by specimens in the collection of the 

 U. S. National Museum, and of H. B. Ward, collected in Nebraska, 

 Iowa, and Maryland, from Colaptes auratus and Melanerj^es erythro- 

 cepholus. 



The type-specimens (from the collection of H. B. Ward, deposited 

 in the U. S. National Museum Helminthological Collection, No. 7235) 

 were collected in Iowa from Colaptes auratus. 



External anatomy. 



The length of this form is 50 to 60 mm., the maximum width about 

 1 mm. 



The head (fig. 1) measures 360 to 380/x long and 320 to 380/x broad. 

 Its anterior portion forms a large protuberance, cylindrical or trun- 

 cate conical in shape, measuring 160/x in length by 150 to 250/x in 

 breadth. The surface of this protuberance, as in Davainea frontina 

 (Dujardin), is thickly covered with minute spines arranged in di- 

 agonal rows. The rostellum i^roper is a muscular bulb, broad (120 to 

 160/^)' and flat, embedded in the anterior end of the spine-covered 

 protuberance. It is armed with a crown of alternating- longer and 

 shorter hooks (figs. 2« and &), 18 and 14/x in length, respectively, 

 and about 400 in number. Instead of being circular the crown of 

 hooks forms a rosette with 8 limbs. 



The suckers are round, 150 to 160|ti in diameter, with their borders 

 armed with numerous booklets (fig. 2c) of varying size up to 10/x, 

 arranged in diagonal rows, 16 to 18 booklets in each row. 



The neck is somewhat narrower than the head, measuring 160 to 

 250/t in breadth, and varying in length according to the state of con- 

 traction (observed maximum 400/x), The first segments are equal in 

 width to the neck and are very short, gradually increasing in both 

 dimensions toward the posterior end of the strobila, where they meas- 

 ure 0.5 mm. in length and 1 mm. in width. The number of segments 



