AET. 21. PAEASITES OP SHAEKS AND SKATES LINTON. 89 



6.18; length of bothrial portion, 0.84, breadth, 1.82; length of neck, 

 4.34, diameter, 0.77 ; length of contractile bulb, 2.30, diameter, 0.21. 



In the specimens collected in 1914 the hooks were not quite so 

 large as in the first lot, the maximum being about 0.10; moreover, 

 one side of the proboscis is densely covered with small hooks, 0.012 

 to 0.024 in length. It should be remarked that the proboscides were 

 almost entirely everted. The proboscides in the first lot were only 

 partly everted; hooks as small as those in the first lot were found, 

 but they were not seen to cover any part of the proboscis as densely 

 as in the second lot. 



Strobile. — Length of longest specimen, in balsam, 26 mm. The 

 first distinct segments are broader than long, soon squarish, then 

 longer than broad ; last segment, with ova, length 2.34, breadth 1.54 ; 

 distance of middle of notch at genital pore from posterior end of 

 proglottis, 0.91. The outline of the proglottides is, in general, 

 rectangular; the last proglottis in the longest strobile is bluntly 

 rounded at the posterior end (fig. 97). 



Reproductive organs. — The genital pores are irregularly alter- 

 nate, situated but little in advance of the posterior third, and 

 are characterized, in adult segments, by having thick, rounded, 

 and slightly projecting lips. The cirrus was not seen everted. 

 but is evidently short and smooth. The cirrus-pouch is oval- 

 elliptical, at right angles to the margin, its length approximately 

 one-third the breadth of the proglottis; vas deferens rather volu- 

 minous, at base of pouch, along median region of proglottis from the 

 anterior border of the ovary to about the middle of the length of 

 the proglottis; testes occupy the median area of the proglottis within 

 the layer of longitudinal muscles. The vagina was not seen very 

 satisfactorily. It appears to enter the cirrus-pouch on the ventral side 

 and is, therefore, difficult to see in whole mounts. In sections it was 

 seen lying on the ventral side of the pouch, and taking a diagonal 

 course in the direction of the ovary. The ovary is two-lobed, some- 

 what dumb-bell shaped, and is situated near the posterior end of 

 the proglottis about midway between the posterior border of the 

 pouch and the posterior end of the proglottis. The uterus, as seen in 

 horizontal sections, lies along the median line, and is more or less 

 sacculated. It was seen to open by a definite pore on the median line 

 near the anterior end of the ventral face of the proglottis; ova, 0.030 

 by 0.015, in specimen mounted in balsam. 



2'y^e.— U.S.N.M., Helm. Coll. 7720. 



Dasyhatis centrura. 



1911, September 14 : A single strobile, attached to the mucous mem- 

 brane near the anterior end of the spiral valve, and a few free prog- 

 lottides, which discharged white masses of ova soon after they had 



