ART. 21. PARASITES OF SHARKS AND SKATES JLUNTON. 81 



RHYNCHOBOTHRIUM UNCTNATUM, new species. 



Plates 7-8, figs. 74-78. 



Scolex with slender, cylindrical neck, and bothria rather widely 

 separated and deeply notched on the posterior border; proboscides 

 long, when fully extended there is a basal, naked portion, succeeded 

 by a few large hooks, 0.075 to 0.12 mm. in length, which are at the 

 base of the hook-bearing portion of the proboscis; next is an inter- 

 val of about 0.11 mm., densely covered with minute hooks, O.OIG mm., 

 ]nore or less, in length, some of them slender and bristle-like, others 

 short and broad; then hooks, similar in shape to the large basal 

 hooks, but not quite so long, appear and continue to the apex of the 

 proboscis. These hooks are, for the most part, nearly uniform in 

 size and shape. They are rather slender and graceful, with a 

 tendency to be rather abruptly recurved at the tip, length about 0.05 

 mm. Sheathes spiral, bulbs long-elliptical with thickish walls, re- 

 tractor muscle attached at base. In a mounted scolex, measuring 

 0.22 mm. in length, a contractile bulb measured 0.56 mm. in length, 

 and 0.14 in breadth. 



Strohile slender, segments beginning very close to the scolex, at 

 first very short, but soon as long as broad, later becoming much 

 longer than broad. In mature segments the length may be as much 

 as five times the breadth. 



Reproductive organs. — Genital pores irregularly alternate at about 

 the anterior fourth, or a little back of that point. Cirrus long and 

 slender ; cirrus-pouch short, fusiform, with a relatively large seminal 

 vescicle on its anteromedian border ; vas deferens unusually volumi- 

 nous, apparently occupying the median axial region from near the 

 anterior border of the ovary to the seminal vescicle; testes dis- 

 tributed throughout the proglottis inside the vitelline layer. 



The vagina was not satisfactorily made out in the whole mounts, 

 and no sections were made. From what is shown in a ripe proglot- 

 tis, in which the uterus occupies the greater part of the interior 

 between the ovary and cirrus-pouch, it would appear that n part of 

 the complex which comprises the folds of the vas deferns may be 

 the vagina filled with sperm, and functioning as a seminal receptacle. 

 What was interpreted to be the distal portion of the vagina was seen 

 lying close to the posterior margin of the cirrus-pouch, but it could 

 be traced for only a short distance. The ovary is bilobed, the lobes 

 being symmetrically placed with respect to the median line. In 

 adult, but unripe segments the lobes of the ovary are longer than 

 broad, in one case, length 0.39, breadth 0.14; in a ripe proglottis, 

 length 0.30, breadth 0.18 ; uterus in ripe proglottides spacious, occu- 

 pying practically all the interior of the segment between the ovary 

 nnd cirrus-pouch and seminal vescicle. The vitellaria have the usual 



