ART. 21. PARASITES OF SHARKS AND SKATES LINTON. 47 



ing, and were somewhat irregular in outline ; shell thin ; 0.10 by 0.08 

 in the two principal diameters. These worms were much broader 

 than those obtained from the black-finned shark on July 13. In 

 other particulars, including the character of the ova, they were in 

 agreement. 



(U.S.N.M., Helm. Coll. 7694.) 



Carcharhmus ohscui'us. 



1914, September 1: 2, lengths 60 and 130 mm. Attached firmly 

 to intestinal wall, the disk embedded in the mucosa. It was neces- 

 sary to dissect it out before it could be removed. 



1916, July 26: 2, scoleces missing, in one of three sharks. The 

 sharks had been dead for some time. The scoleces were searched 

 for with some care, but were not found. The strobiles were slightly 

 macerated. After lying in sea water for a short time large numbers 

 of segmenting eggs were discharged. Length of strobiles, 245 and 

 430 mm. respectively. 



1918, August 5: 19, from one of three 165 centimeter sharks. 

 These were all firmly attached to the wall of the spiral valve; 15 

 were attached in a row, 36 mm. in length ; length of largest 360 mm., 

 with a maximum breadth of 8 mm.; 4 small, immature specimens, 

 in a cluster, length of each 25 mm. 



Scoliodon ten^ae-novae (fig. 7). 



1914, August 20 : 2, lengths 140 and 240 mm. respectively. These 

 agree with D. pileatum^ except that the terminal disk is smaller than 

 the cervical mass. The disk was ivory white, with a diameter of 

 0.80; when extended it was separated from the cervical mass by a 

 constricted portion, 0.22 in length, and 0.60 in diameter; length 

 of cervical mass 0.75, diameter 0.90. The general appearance of the 

 scolex when fixed without compression bears some resemblance to 

 the genus Tylocephalum. 



The scolex was rather actively contractile, and showed a con- 

 siderable variety of contraction phases. 



There is a marked difference between the scoleces of these cestodes 

 from the sharp-nosed shark and those from the dusky shark; the 

 ratio of anterior disk to cervical mass being 0.82 to 140 in the for- 

 mer, and 1.82 to 1.40 in the latter, measurements made on specimens 

 mounted in balsam. A comparison of the strobiles, however, does 

 not reveal differences sufficient to justify referring them to different 

 species. The posterior, ripe proglottides in each become longer than 

 broad. The ova agree in size and appearance, having in each rather 

 thin shells, irregularly collapsed, brownish, with a maximum size 

 of about 0.11 by 0.07 mm. 



