AKT. 21. PAKASITES OF SHARKS AND SKATES LINTON. 13 



Collected in 11 of the years from 1905 to 1918, inclusive: On 4 

 dates in Jul,y: (1) 200 or more, maximum length 20 nmi. ; (2) 30, 

 young strobiles; (3) many; (4) few, in 1 of 3 sharks. On 7 dates 

 in August: (1) to (4) numerous on each date, with large numbers 

 of free proglottides: (5) 2, associated with 3 A. laciniahim and 8 

 P. lasium; (6) 33 in 1, and 3 in another of 3 sharks; (7) 14. On 

 9 dates in September: (1) few; (2) very numerous, with free 

 proglottides, maximum length 20 mm.; (3) 50 or more, with many 

 free proglottides, no other species found; (4)8, with free pro- 

 glottides, from 60-centimeter shark; (5) 20, maximum length 18.5 

 mm., with free proglottides; (6) 95, maximum length 23 mm., a few 

 free proglottides; (7) 200 and over; (8) 8; (9) 1, length 20 mm. 

 On 2 dates in October: (1) many with free proglottides; (2) 6, 

 from 9 to 16 mm. in length. 



(U. S. N. M., Helm. Coll. 7666.) 



Carcharias taurus. 



1905, August 8: 1 strobile with scolex, and easily separating, but 

 mature, segments. 



Galeocerdo arcticus. 



1907, August 7: 5. The scoleces are in agreement with this species; 

 the strobiles are rather longer, about 30 mm., in balsam, than is usual 

 in this species ; little change in the proportions made by the killing 

 fluid. 



1912, August 19 : 2. 



1915, July 31 : Few. 



Galeus glaucus. 



1905, August 5: 20, very small; from spiral valve of young shark 

 about 90 centimeters in length. 



1923, July 23: 52, small, maximum 8 min., from a '^v45-centimeter 

 shark. 



Vulpecula manna. 



1914, July 23 : 10, small, 7 to 10 mm. Dimensions of living speci- 

 men, in sea water: Length, 7.5; bothria, variable, length of one ex- 

 panded and attached to slide, 0.52, breadth 0.45, diameter of acetab- 

 ulum, 0.07 ; distance to first segment 3 ; first distincet segment, length, 

 0.19, breadth 0.18; last segment very variable, approximate length 

 0.70, breadth 0.45. The last segments separate from the strobile 

 easily; length of free proglottis 2.65, breadth 0.78. The ova in this 

 species are characteristically fusiform. 



1922, August 23 : 4. The bothria in this species, as I have usually 

 seen them, are somewhat narrowed in the vicinity of the acetabula, 

 especially while actively extending themselves. In this lot from 

 the thrasher shark the bothria were rather oblong-elliptical, even 



