ABT. 7 CESTODE PARASITES OF BIRDS LINTON 9 



of scolex 0.16, length 0.07; 10 mm. back, breadth 0.35, length 0.14; 

 20 mm. back or scolex, breadth 0.72, length 0.12; 30 mm. back, 

 breadth 1.54, length 0.17; 40 mm. back, breadth 1.90, length 0.17. 

 The anatomy of the proglottides is in close agreement with that 

 already given. 

 From Lams marinus: 



Material not in good condition, but so far as the anatomy is shown 

 it is in agreement with the foregoing; for example, the diameter 

 of the cirrus-pouch is about 0.045 mm., and details of the structure 

 of the genital cloaca, as shown in sections, agree with what was 

 observed in sections of material from other gulls. 

 From Larus argentatus: 



The scoleces differ more or less in shape, due to different con- 

 traction conditions, but not so much in size. Thus a considerable 

 number of scoleces mounted in balsam do not vary much from 

 0.24 mm. in length and breadth. The capitate appendage is mod- 

 erately well developed, although in some of the mounted scoleces 

 it appears to be rather meager. Diameter of cirrus-pouch 0.045 mm. ; 

 number of testes about 22; details of structure of genital cloaca, 

 ovary, vitelline gland, musculature, etc., agree with foregoing 

 descriptions. 



RECORD OF COLLECTIONS 



Sterna hirundo: 



1904, August 3. — Anterior end of strobile, length 7.5 mm.; 

 scolex missing. 



1912, August 2. — Three fragments, aggregating 35 mm. 



1912, August 17.— One, length 135 mm. 



1913, September 4. — Tato, length 145 and 155 mm. 

 Sterna dougalli: 



1904, August 3. — Six fragments of strobile, aggregating 18 mm. 

 Lams atricilla: 



1911, September 9. — One scolex and fragments of strobile. 



1913, August 4. — One, length 52 mm., and fragment. U.S.N.M., 

 (Helm. Coll. 7861.) 



3 mm. ; 1, scolex somewhat macerated, length 38 mm. 



1915, May 27. — Two, one with scolex; length 55 mm. 

 Larus marinus: 



1904, January 19. — Four ; dimensions of one : Length 130 mm. ; 

 diameter of scolex, anterior 0.45, posterior 0.40; length of 

 scolex 0.40. One strobile in this lot, scolex missing, measured 

 250 mm. in length and 2.5 in greatest breadth. 



1911, January 10. — Strobile and fragments aggregating a length 

 of 220 mm. 



1914, April 28.— One. 



10582—26 2 



