772 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [5.4] 



length, 25 ,nm 5 breadth, 1 to 1.5 mm ; genital apertures marginal; cirrus 

 echinate. 



Habitat. — Rhinoptera quadriloba; spiral valve; three specimens; 

 Wood's Holl, Massachusetts, July 20, 1887. 



The three specimens which furnish the data for the present descrip- 

 tion were found in the posterior fold of the spiral valve of the cow- 

 nosed ray (Rhinoptera quadriloba). 



When first placed in sea- water they were rather active. The ex- 

 tended bothria gave the head somewhat the appearance of a peltate 

 leaf. The face of each bothrium is divided into twenty-one pits or loculi. 

 The arrangement of these loculi in every case in the living specimens 

 appeared to be definite and the number constant. There is first a 

 longitudinal row of five comparatively large loculi, occupying the mid- 

 dle line of the bothrium; then a small pit at each end, and seven pits 

 on each side, making twenty-one in all. The loculi are larger towards 

 the posterior end of the bothria than they are in front. In alcoholic 

 specimens the edges of the bothria are curled inwards so that it is not 

 always easy to count the exact number of loculi. The characteristic 

 appearance of a circle of about sixteen loculi around the circumference 

 of the bothrium and a longitudinal row of five at the bottom of the face 

 of the bothrium can be made out in most cases. In one of the speci- 

 mens, when cleared up in oil of cloves, there appeared to be eighteen 

 loculi around the border, which, together with the five central ones, 

 would make twenty-three instead of twenty-one. From this circum- 

 stance I am therefore as yet in some doubt as to whether the number 

 of loculi is always constant. The ribs which outline the loculi are thick 

 and muscular and give to the margins of the bothria a crenulate out- 

 liue. The pedicels are very short and thick. The bothria are lateral, 

 their posterior ends rather thick and slightly flaring. In consequence 

 of this the head of alcoholic specimens is sagittate in marginal, squarish 

 in lateral view. In the living worm, when at rest, the bothria are 

 elliptical. 



The first segments begin as fine transverse wrinkles. In one speci- 

 men the first distinct segments began about l mm back of the head and 

 were .03 mm long and .4 mm broad. What appears to be a characteristic 

 of the species is the occurrence at short intervals of very distinct trans- 

 verse lines which divide the body into pseudo segments. These upon 

 superficial examination might be mistaken for true segments. When 

 examined carefully, however, they are seen to be made up in each case 

 of a number of true segments. In one specimen the first of these trans- 

 verse lines appeared 3.2 mm back of the head, the next 3.8 mm , and follow- 

 ing this two others 5 and 7 mm , respectively, from the head. These pseudo- 

 segments are formed in some cases by the natural division between two 

 segments becoming very distinct, in others by an entire segment be- 

 coming thin and transparent. 



Following are the measurements, in millimeters, of a living specimen: 



