83G KEPORT OF COMMISSIONER OF FISH AND FISHERIES. [H8J 



sheaths spiral ; contractile bulbs long, slender, and parallel. First seg- 

 ments rectangular, broader than long; subsequent segments increasing 

 in length rapidly; posterior end of last segment emarginate. 



Genital aperture of male marginal, about posterior third. Species 

 near R. hispidum, but with relative longer and larger hooks on pro- 

 boscides. 



Habitat. Trygon centrura, spiral valve, July, 1886 ; August, 1887 ; 

 Wood's Holl, Massachusetts. 



In two lots of small Rhynchobothria which were distinguished at the 

 time of collecting by their small size and the occurrence, at least in a 

 majority of them, of two red spots in the neck, in front of the con- 

 tractile bulbs, and which were found to be made up for the most part 

 of the two species R. Mspidum and R. tenuispine, there were two very 

 small individuals which I am obliged to refer to a distinct species. 

 These specimens have lost the posterior segments. The description 

 given rests mainly on the characters of the bothria, proboscides, neck, 

 and first segments. It is probable that there are red pigment spots in 

 the neck as in the two associated species, but this can not be affirmed 

 certainly, since the specimens were not separated from R. Mspidum 

 until after they had been for some time in alcohol. 



The short and broad character of the head may not be true for the 

 living specimens, since the bothria are doubtless mobile. It is to be ob- 

 served, however, that the shape of the heads of these two specimens is 

 unique when compared with the alcoholic specimens of R. Mspidum, 

 although individuals of that species were observed to assume positions 

 while living that were much like that which characterizes R. longispine. 



In the larger specimen of the two the first two segments are rectan- 

 gular, broader than long, the third is nearly square, the fourth is con- 

 siderably longer than broad, while the fifth and last is as long as all the 

 preceding segments taken together; its posterior end is emarginate. 

 The smaller specimen differs from the larger only in having three in- 

 stead of five segments. 



The principal difference between this species and R. Mspidum is in 

 the hooks. These, at least near the base, appear to have the following 

 arrangement: There is first a longitudinal row of broad, stout, abruptly 

 recurved hooks ; second, the row of broad hooks is flanked on either 

 side by a series of long, slender, arcuate hooks arranged side by side in 

 groups of four. Between the two latter series, on the side of the pro- 

 boscis there is a longitudinal space from which hooks are apparently 

 absent. All the hooks are prominent and stand out at nearly right 

 angles to the axis of the proboscis. The following measurements show 

 some of the differences between this species and R. Mspidum : Diameter 

 of proboscis exclusive of hooks 0.02 mm , including hooks 0.05 mnj ; length 

 of broad hooks at base of proboscis 0.01 9 m , breadth 0.019 mm ; length 

 of broad hooks middle of proboscis 0.008 mm , breadth 0.009 mra ; length of 

 slender hooks 0.02 inm , breadth 0.006; distance between transverse 

 spirals 0.02 mm . 



