6 PROCEEDINGS OF THE NATIONAL MUSEUM vol.79 



SQUALONCHOCOTYLE SPHYRNAE, new BpccieB 



Plate 1, Figube 2 



Specific diagnosis. — Squalonchocotyle: Three specimens of a worm 

 from the gills of Sphyma zygaena (hammerhead shark) show a very 

 different body form from these already described and also differences 

 in several details of body structure. The mouth is very large and 

 sunken in the depth of a large, weak sucker with flowing folded mar- 

 gins, which project a little laterally. It communicates at the bottom 

 of this terminal funnel-shaped structure, which can best be appreci- 

 ated from the drawing, with a small pharynx. The body, which 

 measures 8 mm. by 0.5 mm., differs from the others in that the ap- 

 pendix, instead of arising at right angles from the main trunk, is 

 merely a prolongation of the fixation disk. This is not an accident of 

 fixation, for it appears plainly in each specimen, and there is a long 

 projection of the intestinal canal, which runs through the fixation 

 disk to enter the appendix, while the shorter branch turns forward 

 to enter the fixation disk and end between two of the suckers. These 

 large suckers have the usual form and their hooks measure 320/x 

 from tip to tip (fig. 1, e). The hooks are unusual in that their points, 

 which bend almost at right angles, are not so sharply marked off from 

 the trunk as in other forms. In the appendix the booklets are short 

 (48/a) and broadly bifurcated (fig. 1, e'). There has been discussion 

 as to the nature of this appendix. Van Beneden thought the ex- 

 cretory ducts opened through the tips of the two branches, and there 

 have been other ideas, but it is quite plain that the appendix branches 

 at its extremity, the branches ending in rather powerful deep suck- 

 ers, which with the intervening booklets form a sufficiently strong 

 clinging apparatus. The suckers have no relation with excretory or 

 digestive apparatus. They have a deep conical cavity ending in a 

 circular muscular dilatation. 



The genital pore is small, round, and unarmed, and lies in the mid- 

 line, just behind the bifurcation of the intestine. The two vaginal 

 orifices lie just outside the intestinal ceca at this level. The vaginae 

 are very wide, the orifices have a thick hyaline border, which is then 

 surrounded by a band of cells. The uterus runs a straight course 

 but is drawn into short folds. There are six or seven eggs in the 

 uterus. They are large, measuring 200ya by 50;it, with filaments at 

 both ends, which are rather stout and about as long as the egg. 

 There is a long, thick-walled, club-shaped cirrus, which lies dorsal to 

 the uterus and opens with it at the genital pore. It is quite sharply 

 marked off from the long, folded vas deferens. The ovary, which 

 is in the middle of the body, is elongated and folded on itself, and 

 there is a thick-walled receptaculum seminis. The testes lie behind 

 the ovary in about 50 small lobules. 



