22 x^HOCEEDINGS OF THE NATIONAL MUSEUM vol.70 



the proglottis following, length 0.62 on one margin, 0.35 on the other, 

 breadth 0.74) ; posterior proglottis, length 0.63, breadth 0.80. In a 

 lot of small strobiles, 5 to 7 mm. in length, one had the following 

 dimensions: Length 7; 1 mm. back of scolex, length of proglottis 

 0.05, breadth 0.28; 2 mm. back of scolex, length 0.10, breadth 0.28; 

 5 mm. back of scolex, length 0.11, breadth 0.52; 1 mm. from posterior 

 end, length 0.13, breadth 0.57; posterior proglottis, length 0.24, 

 breadth 0.32. The genital apertures are irregularly alternate near 

 the anterior end of the margin of the proglottis. The walls of the 

 genital cloaca are thick and muscular; cirrus-pouch slender, cylin- 

 drical; cirrus not clearly shown in my preparations. What appear 

 to be loops of the vas deferens occupy the inner two-thirds of the 

 length of the cirrus-pouch. There is a voluminous vas deferens, its 

 folds lying on the dorsal side of the cirrus-pouch, and between its 

 inner end and the median line. There is no seminal vesicle. The 

 testes lie posterior to the female genitalia. Their exact number 

 was not detemiined. About 12 was the greatest number observed 

 in transverse sections of about 0.015 mm. thickness. The number 

 is probably about 20. The vagina opens into the genital cloaca 

 posterior to the cirrus. It follows a sinuous course to the median 

 line where it terminates in a subglobular seminal receptacle about 

 on a level with the genital pore. The vitelline gland is bluntly 

 lobed, situated at the median line a little posterior and ventral to 

 the seminal vesicle. In a transA^erse section, 0.56 by 0.50 mm. in the 

 two principal diameters, the vitelline gland measures 0.098 by 0.056, 

 The ovary is profoundly lobed, its divisions being in general pyri- 

 fbrm. It lies in front of the vitelline gland, and is nearly sym- 

 metrical with respect to the median line; its breadth approximately 

 two-thirds the breadth of a mature proglottis. The uterus is at first 

 sacculate. In ripe proglottides the entire medullary space is filled 

 with ova. The ventral excretory vessels are much larger than the 

 dorsal, and are connected by a transverse vessel at the posterior end 

 of the proglottides. The cirrus-pouch and vagina pass between the 

 poral pair of excretory vessels. There are two layers of strong 

 longitudinal muscles, but circular muscles were not seen in any of 

 the sections. 



Following are notes on material referred to this species from other 

 species of gulls : 

 From the herring gull {Larus argentatus) : 



The average breadth of 12 scoleces mounted in balsam, is 0.42, 

 minimum 0.35, maximum 0.52; average diameter of sucker 0.18, min- 

 imum 0.17, maximum 0.22; length of hooks 0.036; number of hooks 

 about 20. An everted rostellum measured 0.21 mm. in length, same 

 as the length of the scolex, diameter at base 0.06, behind hooks 0.04, 



