768 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [50] 



RHINEBOTHRIUM gen. uov. 



['Pa 1 //, a rasp.J 



Body articulate. Head continuous with the body or separated by a 

 neck. Neck merging into segmented body or separated by a constric- 

 tion. Bothria four opposite or in lateral or marginal pairs, faces divided 

 into loculi by several or many transverse and one or few longitudinal 

 muscular partitions, mounted on slender pedicels, very versatile, un- 

 armed, myzorhyuchus none. 



Genital apertures marginal. 



The genus Rhinebothrium is established to accommodate species 

 with echeneiforin bothria, but which have no terminal proboscis of any 

 kind. The presence or absence of such a complicated organ as the 

 myzorhyuchus of Eclieneibothrium appears to one to indicate a generic 

 difference. If this view is correct, then species like Van Beneden's Ech- 

 eneibothrium minimum should be referred to the genus Rhinebothrium. 



10. Rhinebothruini flexile sp. nov. 

 [Plate v. Figs. 3-5.] 



Bothria four, opposite, long, slender, versatile, attached at middle 

 point to head by moderately short pedicels. Face of each bothrium 

 with numerous loculi in two longitudinal rows, forty, more or less, in each 

 row. The slender, free ends of the bothria very versatile, bending 

 readily in any direction, but especially in the plane of the supporting 

 pedicel and axis of the body. An apparent hinge in middle of face of 

 each bothrium opposite the pedicel. No head, strictly speaking, except 

 what is formed by the b itliria and their pedicels. Myzorhynchus none. 

 Neck short, cylindrical, merging imperceptible into the body. Seg- 

 ments begin near the head. First distinct segment broader than long, 

 very soon becoming squarish, then longer than broad ; mature segments 

 six or eight times as long as broad, subcyliudical or fusiform, narrowed 

 at the extremities. 



Genital apertures marginal, about middle of segment; cirrus echi- 



nate. 

 Maximum length 16 mm ; length of posterior segments from 1 to 1.6 mm , 



breadth .2 to .32 mm . 



Habitat. Trycjon centrum, spiral valve, twenty-five specimens, Wood's 

 Holl, Massachusetts, August 10, 1887. 



This species possesses some characteristic features which ally it with 

 Van Beueden's E. minimum from Trygon pastinaca. This is especially 

 true in respect to the shape of the mature segments and the entire stro- 

 bile, in fact, excepting the bothria. The differences shown by the latter, 

 however, are too profound to allow them to be referred to the same 

 genus. This difference can be readily appreciated when it is remem- 

 bered that E. minimum is characterized by having the bothria crossed 

 by eight to ten transverse septan, while R. flexile has in the neighbor- 

 hood of forty. 



