ai:t. 21. PARASITES OF SHARKS AND SKATES LINTON. 55 



bothria. The bothria are really placed on the sides of the scolex 

 which coincide with the flat surfaces of the strobile. 



Following are measurements of a specimen mounted in balsam: 

 Length, 115 mm.; scolex, length, 4.5, breadth, near anterior end, 

 1.33, middle, 0.93, posterior, at base of widely flaring bulbs, 2.24; 

 breadth of strobile at junction with scolex, 1.28, quickly increasing 

 to 1.68 ; distance to first proglottides, 1.54; length of first proglottides, 

 0.07, breadth, 1.96; length of proglottis, 10 mm. from scolex, 0.52, 

 breadth, 1.90; 20 mm. from scolex, length 1.12, breadth 1,88; 40 mm. 

 from scolex, length 2.10, breadth 1.96; length of posterior proglottis 

 5.5, breadth, 1.96. 



Scolex. — The bothria, in alcoholic specimens, ure little, if any, 

 wider than the axial portion of the scolex ; in some of the mounted 

 specimens they are contracted until they are not as broad as the 

 portion of the axis which they enclose. There seems to be a tendency 

 on the part of the bothria to contract strongly. The surface of the 

 scoleces between the bothria and the contractile bulbs is roughly 

 papillate. This is in agreement with the description of the scoleces 

 from Tylosurus raphidoma. This character was not noted in the 

 scoleces from T. acus^ but, upon reexamining a mounted scolex from 

 that host, I find the same character exhibited. The proboscides are 

 rather stout, and are armed with hooks of a variety of shapes and 

 sizes. The proboscis sheathes are slightly tortuous, and the retractile 

 muscle is attached near the proximal ends of the bulbs, which, as 

 is usually the case in this genus, are widely flaring. The scolex, as 

 a whole, is somewhat hour-glass shape, and the posterior end slightly 

 overlaps the beginning of the strobile. Transverse sections of the 

 scolex of the adult and of larval forms show similar structure. 



Strobile. — The strobile is flat and thin, and does not vary much 

 in width throughout its length. The proglottides begin near the 

 scolex, are at first very much broader than long, soon become squarish 

 and ultimately become much longer than broad. The genital 

 apertures are marginal, irregularly alternate, and are placed at 

 about the posterior third of the length. Each is marked by a shallow 

 notch with vertical walls. 



Reproductive organs. — The sectioned material is not entirely satis- 

 factory, but the following points were made out: The common 

 genital pore opens into a shallow marginal notch. The vagina lies 

 behind the cirrus-pouch, and enters the common duct near the 

 marginal aperture. The cirrus-pouch is small, oval-elliptical, and 

 horizontally placed. The vas deferns is voluminous. The testes 

 occupy the entire median axial region, in sagittal sections being 

 interrupted only by the cirrus-pouch and ovary. In a series of 

 sagittal sections, 80 in all, the vagina joins the cirrus at the 6th sec- 

 tion from the marginal genital notch. The cirrus-pouch continues 



