[87] NOTES ON ENTOZOA OF MARINE FISHES. 805 



The ovaries are two oval or elliptical organs, . 17 mm long and .05 ,nm 

 broad, lying one on each side of the median line at the posterior end of 

 the segment. They appear to be confluent at the extreme posterior end 

 of the segment. The granular elements of which they are composed 

 measure .005 mm in diameter. 



A thick-walled tube originates between the lobes of the ovary, and fol- 

 lows the region of the median line in a sinuous course to the posterior 

 edge of the cirrus bulb. It then turns abruptly toward the margin, 

 where it opens into the genital cloaca behind the cirrrus. This tube is 

 evidently the vagina. 



In some of the sections there are to be seen, near the vagina, what 

 appear to be parts of a larger and convoluted tube. This I take to be 

 the vas deferens. It differs radically in appearance from the vagina. 

 The latter in longitudinal sections is linear ; its thick walls inclose an 

 empty space. The former is massive and filled with very fine striated 

 material. This latter appearance, in sections of cestod segments, is 

 occasioned by the presence of spermatozoa. 



Along the margins of the segments, and in the interior among the 

 other organs, there are numerous granular bodies. These are not always 

 of defiuite shape, but are often elliptical, oval, or circular in section. 

 They are probably sections of spheroidal masses. They are from .02 to 

 ,05 mm in diameter, and the granular nuclei with which they are filled are 

 .003 mm in diameter. Some of these bodies, near the margins of the 

 segment, had an incipient striated appearance. They are probably 

 spermatic capsules of the testes, in the nuclear contents of which sperma- 

 tozoa are beginning to be differentiated. There was no indication of 

 ova in these segments. 



tylocephalum, * gen. nov. 



[rvloq, a knob.] 



Body articulate ; head globose ; bothria united into a globular disk 

 and bearing four supplemental disks, which are arranged in lateral 

 pairs ; myzorhynchus also globose, as large as remainder of head. 

 Neck, i. c, unjointed anterior part of body, moderately long. 



Genital apertures marginal (?). 



I have found it necessary to establish this genus to accommodate 

 a single small cestod from the spiral valve of the cow-nosed ray 

 (Rhinopterus quadriloba). As the specimen was associated with a few 

 specimens of Rhinebothrium cancellatum, I at first supposed that it 

 might prove to be the young of that species. The total absence of any- 

 thing like costa3, and, moreover, the presence of supplemental disks, at 

 once shows that it can not be referred to either Echeneibothrium ovBhine- 

 bothrium. 



* See foot-note on page 84. 



