[139] NOTES ON ENTOZOA OF MARINE FISHES. 857 



the base of the proboscides the booklets have only about half the linear 

 dimensions of those at the middle and near the apex. They are simi- 

 lar in shape except perhaps a little more recurved at the point. The 

 booklets are arranged in uniform spirals, which are about 0.01 7 mm apart. 

 Seven hooklets can be seen in each spiral on one side of the proboscis. 



The proboscides bear some resemblance to those of T. bisulcatum 

 (Rhynchobothrium bisulcatum of my former paper), but are much smaller, 

 being about half the diameter, and the hooks are about half as long. 

 The hooks are also relatively more slender. The head and neck of T. 

 robustum also resemble that of T. bisulcatum, but are not so plump. The 

 edges of the bothria were covered with fine capillary bristles as in T. 

 tenue. They were, however, not so abundant, nor were they observed 

 at the apex of the head. 



The segments in all but one of the specimens that I have yet seen 

 were much broader than long. In one, the posterior segments to the 

 number of ten or twelve, are squarish, and the last two or three a little 

 longer than broad. The cirrus bulb in the mature segments extends 

 from the marginal aperture, near the anterior edge, half the distance or 

 more to the median line, and iucliued forward toward the anterior edge. 

 The vas deferens shows plainly, lying in voluminous coils at the base of 

 the bulb and along the median line. The ovary is a broad two-lobed 

 organ centrally placed. The ova lie along the median line. There yet 

 remains much to settle with respect to the disposition of the genitalia 

 of these segments which I have not yet studied from thin sections. 



40. Tetrarhynchus bisulcatum Lt. 



[Plate xiv, Figs. 10-12, and Plate xv, Fig. 1.] 



Rhynchobothrium bisulcatum Lt. Report of U. S. Commission of Fish and 

 Fisheries for 1886, pp. 479-486, Plate iv, Figs. 9-23. 



In my original description of this species I regarded the bothria as 

 two in number, but distinctly bilobed. Since writing the first descrip- 

 tion I have had an opportunity to study living specimens and have de- 

 cided to refer the species to the genus Tetrarhynchus. I was perhaps 

 misled by the close resemblance to Van Beneden's figures of Tetra- 

 rhynchus lingualis Cuv. (Rhynchobothrium paleaceum Bud. and Van 

 Ben., Diesing, Bevis. Ceph. Par., 294). 



The only emendation necessary in the original description is to change 

 from " bothria two, divided into two distinct lobes," to bothria four, ar- 

 ranged in two lateral pairs. Also the female genital aperture is mar. 

 ginal, beside cirrus. 



On the 25th of July, 1887, 1 obtained from the pyloric division of the 

 stomach of a dusky shark (Carcharias obscurus) a large lot of this spe. 

 cies. There were about four hundred of these parasites crowded into a 

 space of 8 or 10 inches in the narrow pyloric constriction of the stom- 

 ach. A portion of this part of the alimentary canal cut open so as to 



