ART. 7 CESTODE PARASITES OF BIRDS LINTON 35 



and all having a tendency to become narrower toward the posterior 

 end. In most cases the segments appear less than 1 mm. back of the 

 scolex; in one strobile, which was about twice as long as the longest 

 of the others, the neck was over 3 mm. in length. The first segments, 

 at first much crowded, and little more than transverse rugae, remain 

 much broader than long, until the posterior end, where, in most 

 cases, they become, for a short distance, slightly narrower and some- 

 what lengthened. Thus, in the longest mounted specimen, measuring 

 about 30 mm. in length, the breadth of segments 0.4 mm. from the 

 posterior and is 0.33 and the length 0.05. The posterior segment is 

 not perfect, but the penultimate segment measures 0.21 in breadth 

 and 0.07 in length. The posterior segment in another strobile was 

 0.10 mm. in length and 0.15 in breadth; 05 mm. from the posterior 

 end the segments were 0.02 in length and 0.28 in breadth (fig. 104). 

 The cirrus and cirrus-pouch are rudimentary, but it can be seen 

 that the reproductive pores are unilateral. Rudiments of a seminal 

 vesicle appear in the posterior segments of some of the strobiles as a 

 slightly sinuous mass Avhich lies along the anterior border of the seg- 

 ment to a point about half way between the median line and the 

 aporal margin. The three testes are small and placed near together 

 in the postero-median part of the proglottides. 



The agreement in number, size, and character of the hooks with 

 H. fusus is close; the size of the strobile, however, is much less. 



RECORD OF COLI.ECTION 



Larus argentatus^ new^ host : 

 (U.S.N.M., Helm. Coll. 7875.) 



1912, July 22. — Fifteen with scoleces. 



1913, January 6. — One strobile, scolex missing, very slender; 

 length 26 mm. 



1913, November 21. — Two; anterior end of strobiles exceed- 

 ingly attenuate. 



1914, January 20. — Two, very slender. 



1914, September 8. — Few scoleces, several fragments, maximum 

 length 100 mm., greatest breadth 1.5 mm. ; anterior ends ex- 

 tremely attenuate. 



1914, September 18. — One with scolex, length 55 mm., and frag- 

 ments of about five strobiles. 



1914, December 23. — One strobile with scolex from small gull. 



1915, January 29, — Many fragments representing about eight 

 strobiles, maximum length 34 mm., one scolex. 



1915, April 5. — One scolex, and fragments of about three stro- 

 biles, maximum length 20 mm. 



