[5] NOTES ON ENTOZOA OF MARINE FISHES. 723 



shouldered behind, and tapering to a blunt point in front. Two very 

 deep fossae which are marginal with respect to the head, lateral with 

 reference to the body, divide the head into two leaf-like lobes, with 

 thin flexible borders. When the edges of the lobes are closely ap- 

 pressed the fossa) appear as marginal slits. The fossa) extend to the 

 apex of the head but do not unite. Each fossa is continuous behind 

 the head with a narrow median fun ow. 



The body near the head is quite narrow, almost cylindrical, or a little 

 flattened on the margin to correspond with the greater marginal diam- 

 eter of the head. It is very much narrower than the head. The seg- 

 ments begin immediately behind the head, where they are short and 

 thick and very much crowded. They increase in length slowly until 

 about the posterior third where they are nearly square. The segments 

 of the posterior third are nearly square and quite thin. The body is of 

 nearly uniform breadth throughout its entire length. 



Genital apertures lateral near middle of segment, male and female 

 approximate. Aperture of oviduct on opposite lateral face of strobile 

 near anterior edge. 



Maximum length 7G5 mm ; breadth of body l.S mm ; breadth of head 2.5 mm . 



Habitat. — Tylosurus caribbwus, intestine. Buzzard's Bay, Massachu- 

 setts, July 27, 1886. Four specimens. 



Three of the specimens were very slender, almost filiform, the other 

 was more contracted and consequently thicker, but it, too, was of nearly 

 uniform size throughout. 



The shortest specimen measured about 64 mm in length when lying 

 undisturbed in water. When taken by the posterior end and lifted 

 slowly from the water, allowing it to stretch out to its fullest extent by 

 its own weight, it increased in length to 240 mm . The largest specimen, 

 measured in the latter way, was 665 mm in length. After lying in sea- 

 water for twenty-four hours it was again measured and found to be 

 765 mm in length. After being preserved twelve months in alcohol it 

 jtill measures 720 mm in length. The other specimens while living meas- 

 ired 215 and 262 mm respectively. 



The genital apertures are lateral; on the larger specimen the follow- 

 ing points were made out with no other aid than a simple lens : On one 

 of the lateral faces openings occur on the middle of the segments along 

 the median line. These apertures were traced to within l(>0 nim of the 

 head, where they merged into a median lateral groove; the latter is con- 

 tinuous with one of the marginal fossa) of the head ; on the opposite 

 lateral face there is a small opening or pore near the anterior edge of 

 each segment ; these pores are not usually exactly on the median line 

 of the strobile, but stand a little to one side or the other and thus make 

 an irregularly sinuous line ; they were traced to within 240 mm of the 

 head, where they become indistinguishable in the median groove; the 

 latter, like its fellow on the opposite face, extends to the head, where 

 it is continuous with the other marginal fossa of the head. 



