[105] NOTES ON ENTOZOA OF MARINE FISHES. 823 



Two of the posterior segments were stained with red and green ani- 

 line and a few additional points in the anatomy were made out. The 

 vagina was traced from the posterior end of the segment along the 

 median line in a "straight course to about the anterior third, where it 

 turned toward one of the margins, then back a little, and opened be- 

 side and in front of the cirrus, which, retracted in its bulb, lay in the 

 bend of the vagina. 



The cirrus bulb is oblong and apparently constantly angled or bent 

 about the middle. That is, the cirrus bulb, from the marginal aperture, 

 is inclined inward and backward. At about half its length it turns so 

 that the inner end is inclined inward and forward. The length of the 

 cirrus bulb, in one of the posterior segments, is about .22 Ium ; its diame- 

 ter .055 mm . 



When the segments were cleared up in oil of cloves the ovaries be- 

 came visible at the posterior end, lying one on each side of the median 

 line and separated from each other by the vagina, which at this point 

 wae somewhat enlarged. 



THYSANOCEPHALUM, gen. nov. 



PhyUobothrium, spec. Linton. 



Body articulate, tseniaefonn. Head separated from body by neck, 

 very small, quadrangular, with four sessile bothria, each armed with 

 two simple hooks and provided with a single loculus in front of hooks. 

 Neck at first slender, then expanding into a voluminous mass of lobed 

 and crisped folds. Genital apertures marginal. 



I was led into error in my original description of the Cestod upon 

 which this genus is founded by its singularly close resemblance to Van 

 Beneden's PhyUobothrium lactuca (Vers. Cesto'ides, Plate iv, Figs. 1-7). 

 What was taken to be a rostellum, and so described by me, was present 

 only in the smaller specimens of the lot. This so-called rostellum 

 proves, upon subsequent examination, to be the true iScolex. The 

 sketches of this organ (see Notes on Entozoa, U. S. Fish Commission 

 Report for 1886, Plate n, Figs. 7, 7a, and 76) are misleading, particu- 

 larly with regard to the hooks. The scolex is very small in comparison 

 with the cervical ruff which follows it and which increases in size with 

 the age of the strobile, while the scolex of the adult is no larger than 

 that of young specimens. 



26. Thysanocephalum crispum Lt. 



PhyUobothrium thysanocephalum Lt., Report of U. S. Commissioner of Fish and 

 Fisheries, 1886, pp. 464-468, Plate n, Figs. 1-12. 



Scolex very small, minute when compared with the cervical ruff or 

 pseudoscolex of an adult specimen, quadrangular in outline and pro- 

 vided with four oblong bothria. Each bothrium is divided about the 

 anterior third into two loculi by a thick, transverse, chitinous (?) parti- 



