[77] NOTES ON ENTOZOA OF MARINE FISHES. 795 



Habitat. — Trygon centrum, spiral valve, two specimens; August 1, 

 1887, Wood's Holl, Massachusetts. 



The specimens were immature. The larger afforded the following 

 measurements while living: 



Millimeters. 



Length 17.00 



Length of bothxia CO 



Breadth of hothria 50 



Diameter of pedicel 14 



Diameter of head at base of pedicels 46 



Diameter of neck immediately back of head 16 



Diameter 4 m,n back of head 12 



Distance to first distinct segment CO 



Length of first distinct segment 04 



Breadth of first distinct segment 12 



Length of last segment 1.60 



Breadth of last segment 28 



As the measurement ,4 mm back of the head shows, there is a slight 

 narrowing of the body at that point. There is, in fact, a slight con- 

 striction, for the diameter immediately increases again from .12 to 

 .14 Ium . In the alcoholic specimen the breadth of the head, including 

 the bothria, is .8 mm , the length .6 ,nm , diameter of the anterior part of 

 the body ,14 mra , length of posterior segment 1.16 mm , breadth .3 mm . 



The posterior segments are not mature. They agree very nearly, 

 however, with the median segments of S. variabile. The segments in 

 question are slender, rectangular with slightly rounded angles. The 

 ovaries lie at the posterior end of the segment on either side of the 

 median line. The two oblong oval lobes are confluent at their posterior 

 ends and exteud forward along the margins to the vicinity of the cirrus 

 pouch. The latter is not yet clearly defined, but enough to show that 

 the genital apertures are marginal and situated about the posterior 

 burth. In front of the genital aperture the interior of the segment is 

 filled with the globular spermatic capsules of the testis. They are 

 ,bout .04 mm in diameter. Along each margin inside of the muscular 

 all there is a narrow space filled with small granular bodies. This 

 pace is limited on the inner side by the slightly sinuous aquiferous 

 essels. 



The resemblance of the strobile of this species to Spongiobothrium 

 ariabile is so close as to lead me to suspect that it might be the youug 

 f that species. The lacinio-crispate bothria of 8. variabile might easily 

 e conceived to develop from the simpler leaf-like bothria of Antho- 

 eplialum gracile. The fact, however, that the bothria in S. variabile 

 re in distinct lateral pairs, while in A. gracile they are almost cruci- 

 brmly disposed, reveals a difference so profound that it is not only ex- 

 remely unlikely that the one form should follow the other in the same 

 ndividual, but is sufficient to create a just doubt as to whether that 

 ould be a true classification which would refer them to the same 

 enus. Moreover, no supplemental disks have been discovered in J3. 



