i So Papers from the Marine Biological Laboratory ai Tortugas. 



The general outline of the head and neck of this species bears a strong 

 resemblance to that of Otobothriuni crcnacollc. There are no accessory 

 organs on the bothria, however, and the contractile bulbs do not diverge at 

 their posterior ends ; furthermore, the bothria correspond in position to the 

 lateral margins of the strobile instead of to the flat surface. 



From the tiger-shark (Galeoccrdo tigrinus), June 2, five, spiral valve. 

 See remarks under TJiysanocephalus (pp. 164, 167). 



LARVAL STAGE. 



On July ii a small amber-colored cyst was found on the viscera of a 

 black grouper (Mycteroperca bonaci). The cyst contained a blastocyst in 

 which was a small larva which appears to belong to this species, although 

 the general appearance, not only of the larva, but of the cyst as well, was 

 almost identical with that of the larva and cyst of 0. crenacolle. There 

 is, however, no indication of accessory organs on the bothria, while the 

 hooks, thick-margined bothria, short neck, and undivergent bulbs, all agree 

 with the species from the tiger-shark. 



Measurements of living specimen, in millimeters : Cyst, length 0.84, 

 breadth 0.50; blastocyst, length 0.32, breadth 0.18; larva, length 0.16, breadth 

 0.08. 



On July ii one larva of this species was obtained from a cyst on the 

 viscera of a grouper (Epincphelus striatus~). 



22. Rhynchobothrium exile sp. nov. 



(Plate /. figs. 48-54.) 



Bothria with thin, flexible margins, thus giving to the preserved speci- 

 mens a variety of shapes, nearly parallel in marginal view, with posterior 

 ends sometimes slightly divergent. Neck two or more times the length of 

 the head, cylindrical, and as wide as or wider than the body, and thicker; 

 bulbs long-oval or elliptical, sheaths' in close spirals; proboscides long, only 

 the basal portions seen everted ; bulbous enlargement at base of proboscis 

 armed with many small and a few large hooks. On the everted part of the 

 proboscis the hooks are of very diverse shape and size, on the inverted part 

 they appear to be more regular in shape than they are at the base. Body 

 linear, filiform; first segments begin near base of neck, at first very short, 

 increasing in length rapidly, ultimately becoming many times as long as 



