A PARASITE OF THE TIGER SHARK. 
545 
The latter constitute an abrupt expansion into a large, lobed, crisped, 
and folded mass, which, in alcoholic specimens, is more or less globose 
or disciform, but in living specimens may be spread out into a flat suc- 
torial disk with fimbriated edges. This organ is so conspicuous and 
takes the place of b'otliria so effectually as an organ of adhesion that it 
may be called with some degree of propriety the pseudoscolex. The 
diameter of this organ may be from five times, in small specimens, to 
thirty or more times in adult specimens the diameter of the scolex. 
Behind the pseudoscolex the body is broad, somewhat flattened, trav- 
ersed by deep longitudinal rug®, covered by fine transverse stri®. The 
unjointed part of the body is long and nearly linear/ The segments 
begin remote from the head, at first as transverse wrinkles ; subse- 
quently they decrease slightly in breadth and increase gradually in 
length. Near the posterior end they are squarish and at the extreme 
posterior end two or three times as long as broad. The free proglottides, 
are oblong, truncate posteriorly, anterior angles rounded, and usually 
appressed and surmounted by a rounded tip at the anterior end, often 
breaking away before ova are developed, ultimately becoming much 
elongated. 
Genital aperture a marginal cloaca. Cirrus long with spinose base. 
Length of strobile as much as 1 metre. 
Varieties . — There are two types of the adult specimens based on the 
character of the pseudoscolex. In one there are several, six or eight, 
primary folds radiating from the scolex, each primary fold being made 
up of a number of smaller secondary folds. This type is rather poorly 
represented by the specimen sketched in fig. 1, which is from a small 
specimen where the distinction is not so strong in this particular as in 
the adult. A better example is figured in the author’s Notes on 
Entozoa, U. S. F. C. Report, 1886, plate n, fig. 1. 
The second type has a much more compact pseudoscolex, and the 
radiating folds are illy defined, fig. 7. These types are probably due to 
different degrees of contraction of the strong longitudinal muscles, 
many of which enter the pseudoscolex direct from the body without 
passing through the neck proper. 
Emendation of original description . — The specimens which were ob- 
tained in the first find did not exhibit any movements of the scolex. 
The scolex was observed only in the smaller specimens, where it ap- 
peared to be a rigid body of chitinous structure and in some instances 
became detached during the examination of the fresh specimens. The 
scolex was not observed in the larger specimens, though doubtless 
present in all, the neck beiug contracted and the scolex buried among 
the small folds of the apex of the pseudoscolex. Furthermore the 
specimens were among the first of this difficult group which the author 
attempted to identify. Hence au inexcusable, though not unnatural, 
mistake was made in regarding the scolex as a hooked rostellum, char- 
acteristic of young specimens, but an evanescent character lost in the 
H, Mis, 274 35 
