48 PEOCEEDINGS OF THE NATIONAL MUSEUM vol.70 



collecting. The rostelliim is short and broad ; the hooks, 10 or 12 in 

 number, are 0.015 mm. in length (fig. 149). 



Measurements made at the time of collecting, specimen slightly 

 compressed : Length 12 mm. ; diameter of scolex 0.22, length 0.22 ; 

 diameter of rostellum 0.08; diameter of neck 0.10; distance to first 

 distinct segment 0.12; length of first distinct segment 0.02, breadth 

 0.16; length of last segment 0.12, breadth 0.60; length of fourth from 

 last segment 0.09, breadth 0.90 ; number of segments 250. 



HYMENOLEPIS, species 



Figures 15.3-156 



Among the cestodes collected by Vinal Edwards is a small lot from 

 Larus delawarensis^ collected January 24, 1914, U.S.N.M., Helm. Coll. 

 7884. My note made at the time of a preliminary examination of 

 the formalin material is: Slender cestodes with distinct segments; 

 diameter of scolex 0.45 mm.; numerous short fragments from 10 to 

 15 mm. in length; longest strobile, scolex missing, 50 mm. 



The mounted material comprises two scoleces and six fragments 

 of strobiles which represent two strobiles 30 and 44 mm, in length 

 respectively. The proglottides are all immature. 



Scolex. — Somewhat pyramidal, rostellum longer than scolex, taper- 

 ing to the middle of its length, enlarged at the apex, which bears a 

 single crown of 10 hooks, 0.054 to 0.060 mm. in length. The hooks 

 have long dorsal and short ventral roots, blade but slightly recurved, 

 and are longer and less slender than those of H. ductilis from the 

 herring gull. 



Strohile. — There is a short neck, about as long as the scolex. For 

 a short distance the segments are closely crowded, but soon become 

 distinct, and, in places, as long, or even a little longer than broad. 

 Throughout the greater part of the strobile the proglottides have 

 abruptly flaring posterior borders. Near the posterior end of each 

 strobile the proglottides are, for a short distance, crowded and much 

 broader than long. Only rudiments of the genitalia have developed, 

 but are sufficient to show that the genital pores are unilateral and 

 near the anterior end of the proglottis. 



Dimensions of larger specimen in balsam: Lenth 44.00 mm.; 

 diameter of scolex 0.32, of sucker 0.14; length of rostellum 0.25, of 

 hooks 0.054; breadth of neck 0.19; length of proglottides 0.5 mm. 

 from scolex 0.015, breadth 0.18; length near middle of strobile 0,15, 

 breadth 0.21; length 1 mm. from posterior end of strobile 0.08, 

 breadth 0.42; length of last proglottis 0.15, breadth 0.26, 



