32 PEOCEEDINGS OF THE NATIONAL MUSEUM vol.70 



segment. The length of the cirrus-pouch is about 0.35 mm. and its 

 diameter, maximum, 0.07. The cirri were retracted. They appear 

 to be smooth. The vas deferens is straight with rather rigid walls 

 from a point a little mediad of the middle of the length of the cirrus- 

 pouch to its lateral extremity, where it opens into the genital cloaca 

 near the entrance of the vagina. The cirrus could not be made out, 

 but it appears to be represented by a recess in the anterior wall of 

 the genital cloaca (fig. 93) corresponding to Wolff hiigel's figure.- 



KECOED or COLLECTIONS 



Oideiiiia perspicillata^ new host : 



1913, May 8. — Six larger, length about 128 mm., breadth 2; 

 6 smaller, length from 15 to 25 mm. 



(U.S.N.M., Helm. Coll. 7873.) 

 Glaucionetta clangula aviei'icana^ new host : 



1914, December 28. — Two strobiles, 33 and 52 mm. in length, no 

 scoleces. 



HYMENOLEPIS DUCTILIS, new species 



Figures 94-101 



Certain small, slender taenioids from the herring gull, suggesting 

 H. 7nicrosoma (Creplin), but differing from that species in the 

 smaller size and the shape of the hooks, in the smaller and less lobed 

 ovary, and the more slender cirrus-pouch, are here referred to a 

 new species. 



ScoUx. — Somewhat pyramidal, breadth, in balsam, about 0.2 mm. ; 

 suckers oval-elliptical, a little longer than broad, for example, length 

 0.12, breadth 0.10, average diameter in balsam 0.11; rostellum much 

 longer than scolex, slender with single crown of hooks, 10 in num- 

 ber, length about 0.039, rather slender, ventral root short, dorsal root 

 long and slightly curved at the tip, blade much shorter than ventral 

 root. 



Strobile. — Small, slender; neck short, segments at first very short, 

 increasing in length and breadth slowly, but throughout much 

 broader than long. Thus, the posterior, ripe proglottides in a 

 strobile mounted in balsam, measured 0.07 in length and 0.35 in 

 breadth ; lateral margins usually sharply serrate. The genital pores 

 are unilateral, and situated toward the anterior end of the margin. 

 The cirrus-pouch is C3dindrical, or long-fusiform, usually more or 

 less curved or spiral, in earlier portions of the strobile extending to 

 the median line, or beyond it; in a proglottis measuring 0.33 mm. 

 in breadth, the cirrus-pouch measured 0.17 in length and 0.024 in 



2 Kenntniss der Vogel helminthen, flg. 103. 



