180 = Papers from the Marine Biological Laboratory ai Tortugas. 
—— Zz | | 
Segment. Length. | Breadth. | Segment. Length. | Breadth. 
I 0.02 O.1I 7 | 0.16 0.16 
2 03 II 8 220 17 
3 | 05 12 | 9 43 19 
4 | 06 -14 10 .62 24 
5 | II 16 | II 72 30 
6 12 16 || 12 1228 32 
The general outline of the head and neck of this species bears a strong 
resemblance to that of Otobothrium crenacolle. 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 (Galeocerdo tigrinus), June 2, five, spiral valve. 
See remarks under Thysanocephalus (pp. 164, 167). 
LARVAL STAGE. 
On July 11 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 O. 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 11 one larva of this species was obtained from a cyst on the 
viscera of a grouper (Epinephelus striatus). 
22. Rhynchobothrium exile sp. nov. 
(Plate 7, 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 iong as 
