ABT. 7 CESTODE PABASITES OF BIRDS LINTON 7 



Genus TETRABOTHRIUS Rudolphi 



For synonymy see Ransom's Taenioid Cestodes of North American Birds, Bull. 

 69, U. S. Nat. Mus., 1909. 



Scolex provided with four prominent suckers in dorso-ventral 

 pairs, and with a characteristic cap-lilce appendage at the anterior 

 end. Proglottides begin near the scolex, and, as a rule, are much 

 broader than long. The genital pores are unilateral, each consisting 

 of a strong muscular cloaca into which the cirrus and vagina open. 

 The cirrus-pouch is small, much smaller than the cloaca, on the 

 inner border of which it lies. The vitelline gland lies in front of 

 the ovary. 



TETRABOTHRIUS CYLINDRACEUS (Rudolphi) 



Figures 6-13. 



Cestodes in the collection from two species of tern and three 

 species of gull, belonging to the genus Tetrabothrius^ while exhibit- 

 ing considerable difference in the appearance of the strobiles, agree 

 in so many respects that the best disposal of them seems to be to 

 place them in the same species. Further details are given under 

 each specific host. Differences in the structure of the scoleces were 

 slight, although there were considerable differences in size. The 

 genital pore in adult proglottides was at about the middle of the 

 length, or a little anterior to the middle, and nearly on the margin. 

 The diameter of the cirrus-pouch was nearly the same in all, and the 

 relation between the vagina and cirrus at the point of entry into 

 the cloaca was the same in all. The number of testes, which sur- 

 round the ovary, appeared to be about the same in all. The number 

 of fibers in the bundles of longitudinal muscles did not furnish a 

 reliable specific character, since the number of fibers differs in 

 different regions of the strobile, and in different parts of the same 

 section. In all of the sections there is close agreement in the 

 nature of the longitudinal muscles. In all cases there are two 

 quite distinct layers, an inner layer of relatively large bundles, with 

 25 fibers, more or less, in each, and an outer layer consisting of 

 a greater number of bundles than are found in the inner layer, 

 but with from 3 to 7 fibers in each. Mature ova were seen only in 

 sections of material from the tern. They were surrounded bj^^ thin, 

 membranous envelopes. 

 From Sterna hirundo^ new host : 



Appendage of scolex moderately developed; length of scolex, 

 0.24; breadth, anterior, 0.24; posterior, 0.32, in balsam. 



Maximum length of strobile 55 mm.; posterior segments, length 

 1, breadth 2; margins of strobile rather sharply serrate, except in 



