ART. 7 CESTODE PAEASITES OF BIRDS LINTON 17 



spines are nearly straight, with abruptly recurved tips, and with 

 strong basal supports ; length about 0.004 mm. They are very closely 

 placed — about 20 counted in the space of 0.015 mm. — in a sinuous 

 row following the scalloped border of the rostellum. The suckers 

 are armed with sharp-pointed hooks, most strongly represented on 

 the anterior border, but sparingly placed elsewhere on the sucker; 

 length 0.008 mm. Diameter of scolex in balsam 0.28. 



Strobile. — The segments begin very close to the scolex, at first 

 much broader than long, with the posterior edge slightly projecting 

 and rounded at the lateral margins. <As the segments lengthen 

 the posterior edges give to the lateral margins a serrate outline. 

 Genital pores irregularly alternate, about the middle, or a little in 

 front of the middle of the lateral margin ; cirrus-pouch cylindrical, 

 reaching nearly to the median line. The testes are at the posterior 

 end of the proglottis behind the female genitalia. Their number was 

 not satisfactorily made out, but there appear to be about nine. The 

 vagina lies close behind the cirrus-pouch. It was traced to the 

 median line where it was obscured by the ovary. The ovary is oval, 

 transversely placed a little in front of the middle, and occupies 

 about two-thirds of the breadth of the proglottis. Immediatelj'^ be- 

 hind it, at the median line, is the vitelline gland which appears in 

 dorso-ventral view to be fusiform. In a proglottis 0.27 mm. in 

 breadth the vitelline gland measured 0.054 by 0.018 mm. in the 

 two principal diameters. Ripe proglottides are as long or longer 

 than broad. The uterus occupies all the medullary space in the 

 ripe proglottides. The ova are nearly circular in outline, with thin, 

 membranous shells; diameter of onchosphere about 0.02 mm. 



Dimensions of a strobile with ripe proglottides, in balsam : Length 

 10; breadth of scolex 0.25. length 0.21; diameter of sucker 0.08; 

 breadth of rostellum 0.16; breadth of neck 0.12; length of segment 

 1 millimeter back of scolex 0.10, breadth 0.15; length of segment 

 5 millimeters back of scolex 0.32, breadth 0.32; length of segment 

 near posterior end 0.58, breadth 0.35. Dimensions of small strobile : 

 Length 3; breadth of scolex 0.29, length, 0.17; breadth of neck 0.11 ; 

 length of segment 1 millimeter back of scolex 0.08, breadth 0.32; 

 length of segment near posterior end 0.25, breadth 0.37. 



RECORD OF COLLECTIONS 



Larus atHciJla, new host: 



1914, September 29. — One scolex, and fragments of 2 strobiles; 

 longest 40 mm., in formalin. 



1915, May 18. — Twenty-eight short strobiles, from 2 to 4.5 mm. 

 in length, with scoleces. 



(U.S.N.M., Helm. Coll. 7865.) 



