AKT. 21. PARASITES OF SHARKS AND SKATES LINTON. 33 



gether; namely, Anthohothrium laciniatum, Crossohothrium angus- 

 tuni^ and Phorelohothrium, lasium. These cestodes have a similar 

 habit with respect to the ripening of the proglottides. In each 

 species the proglottides separate from the strobile before maturity. 

 They continue to grow after separation from the strobile. Often 

 the chyle of the spiral valve was found to be swarming with free 

 proglottides of these three species. The ova are very different, one 

 species from the other. Thus, in A. laciniatum they are nearly cir- 

 cular in outline, in G. angustum they are fusiform, and in P. las'mm' 

 they are as described above. Further details are given under C. 

 milherti below. 



Following are dimensions of four specimens mounted in balsam : 



Lengtli of strobile 40.00 15.00 25.00 18.00 



Breadth of scolex, excluding projecting hooks- 0. 39 0. 34 0. 38 0. 25 



Length of scolex 0. 51 0. 34 0. 34 0. 30 



Length of longest hook 0. 10 0. 10 0. 10 0. 11 



Length of spines on neck, maximum 0. 015 0. 015 0. 018 0. 018 



Distance to first distinct segment 2. 50 2. 80 1. 12 2. 10 



Length of posterior segment 2. 20 1, 20 0. 77 0. 50 



Bre.Tdth of posterior segment 0.84 0.35 0.45 0.25 



Following is a list of finds of this cestode not hitherto recorded. 

 All are from the Woods Hole region, and all from the spiral valve 

 of the host. 



Garcharhinus commersonii. 



1922, August 5: 6, associated with 1 G. angustum, in a 135-centi- 

 meter shark, brought to the laboratory by Otis Luce, and identified 

 by Dr. H. M. Smith ; menhaden in stomach, beak and lenses of squid 

 in spiral valve, also a structure which appears to be decalcified and 

 partly digested spines of a small sting ray. August 7 : 17, associated 

 with 2 A. laciniatum and 3 G. angustum; many free proglettides ; in 

 a 135-centimeter shark; menhaden in stomach. 



1923. On 10 dates in August and 1 in September, in 16 sharks, 

 many, few, 54, 10, 115, 134, 2, 7, 1, 30, 197, 9, 119, 164, 1, 3; maximum 

 length 59 mm., usual length 25 to 30 mm. 



Garcharhinus limbatus. 



1915, August 6 : 7, associated with 175 G. angustum. 



r918, July 13: 4, associated with 14 Discocephalum fileatum,; in 

 210-centimeter shark ; lenses and otoliths of fish in spiral valve. 



Garcharhinus inilberti. 



1915, August 12 : Many in each of 5 sharks. August 18 : Many. 



1916, September 25: 2. 



1922, July 3: 185, in one of two sharks; fragments of squid in 

 spiral valve. 



