[17] ENTOZOA OF MARINE FISHES OF NEW ENGLAND. 469 



•It differs f'-oin 0. versatile, however, in being much smaller, and in 

 the proportions of the segments. In 0. versatile the segments are 

 square, while in 0. angustum all the segments are long and narrow. 



The following measurements were made from mounted specimens : 



Dimensions: 



No. 1. 



No. 2. 



mm. mm. 



Length of strobile 17. no 18.00 



Length of bothrium 0. t;4 j 



Breadth of bothrium, widest part j 0.32 i 



Breadth of neck near head 0. 14 I 



Length of neck | 5. 00 



Length of posterior segment ' 2. 20 2. 00 



Breadth of posterior segment 0. 44 0. 28 



Xo. 3. 



mm. 

 20.00 



2.46 

 0. 54 



The anterior supplemental disk (auxiliary acetabulum) is small and cir- 

 cular and is quite manifest. I must confess, however, that the identifica- 

 tion of the other was not wholly satisfactory. An oval disk was distin- 

 guished in a few. In some heads stained with carmine, eosin, and hrema- 

 toxylon, respectively, they cannot be distinguished. At about the ante- 

 rior third the face of each bothrium, in the stained specimens, is crossed 

 by a curved fibrous band which is concave in front. This band lies in 

 the tissue of the bothrium and is not raised on the surface. It seems to 

 be connected with another band lying farther back in the bothrium and 

 deeper in its substance. If they are connected they probably make the 

 oval border of the second disk. If one is to judge from the specimens in 

 this lot— about fifteen in number— the secondary disk in the center of the 

 bothriais an extreme doubtful character. It is plainly different in its 

 nature from the anterior disk which was differentiated from the adjacent 

 tissue cleLx'ly, both in unstained and stained specimens. The fine trans- 

 verse strife on the neck, which may be distinguished also on the mature 

 proglottides, are a more characteristic feature of this worm than the 

 second disk (auxiliary acetabulum). 



The genital organs open nearly opposite the anterior fourth of the 

 proglottis, on the margin. 



The vagina can be traced from the posterior end of the segment, 

 where it originates as a coiled tube, lying between the two marginally 

 placed ovaries. It lies along the central line of the segment, until a 

 short distance in front of a point opposite the vaginal opening, where 

 it turns, forming a crook-shaped curve, and opens in front of the penis. 

 The latter organ and the testis lie in the curve of the crook. 



Habitat. — Dusky Shark (Garcharias obscurus), in spiral intestine. 

 Wood's Holl, Mass., August, 1884. 



Crossobothrium,* gen. nov. 



Body articulated, slender, flattened, subquadrate; neck short or 

 none; bothria four, opposite, pediceled, unarmed, each provided with 



*Kpv66oi= a border, fringe. 



