106 AVIAN ENTOZOA—LINTON. 
atozoa already developed and developing. Ovahad not yet made their 
appearance. Sinuous marginal aquiferous vessels, as well as very 
strong fascicles of longitudinal muscles were continuous from segment — 
to segment. 
Naturally Krabbe’s Tenia dodecacantha from Larus minutus is sug- 
gested by this variety, but that species must be excluded from consid- 
eration on account of the character of the spines, which in Krabbe’s 
species are from 0.72 to 0.74 millimeter in length instead of 0.12 milli- 
meter. 
Tenia filum Goetze. 
(Pl. vi, Figs. 72-78. ) 
Diesing, Syst. Helm., p. 530; Sitzb., x11, p. 607, and X1rx, p. 411. 
Dujardin, Hist. des Helm., p. 605. Krabbe, Bitrag til Kunds. om Fugl. Bend., 
p. 312, 313, Pl. vii, Figs. 198-201. 
Head subglobose, broader than long; bothria nearly circular; pro- 
boscis cylindrical, enlarging at the extremity, with a circle of small ab- 
ruptly recurved and sharp-pointed hooks, the slender pointed part of 
the hook parallel with the basal portion and a little longer; neck long 
and slender; ripe segments subcuneate, posterior marginal edges 
usually prominent and acute; genital apertures near one of the mar- 
gins, cirrus slender, tapering, smooth from a swollen spinous basal 
portion. 
Longest specimens observed 52 millimeters in length. Length of 
hooks 0.025 millimeter. 
HABITAT: Larus californicus, intestines, Yellowstone Lake; obtained 
on two different occasions, August 2 and 10, 1890. 
The following dimensions are in millimeters. In one specimen, 
measuring 52 in length, the diameter of the head was 0.2, of the neck 
0.1; length of the last segment 0.12, breadth 0.44. In another speci- 
men the diameter of the proboscis at the apex was 0.08, at the base 
0.06; diameter of head 0.27, length 0.22; diameter of neck 0.15 ; length 
of first segments 0.02. breadth 0.12; diameter of bothrium 0.11. 
The diameter of the spinous basal portion of the cirrus was in one 
instance found to be from 0.012 to 0.015; diameter of filiform terminal 
portion, near the base, 0.006, tapering to 0.004 at the extremity ; length 
of filiform portion 0.05, of spinous basal portion 0.08. 
The segments in some specimens were rather crowded with margins 
somewhat rounded making convex serrations on the margins. The re- 
productive apertures were in these cases not immediately at the mar- 
gins, but at a distance from the nearest margins equal to one-third the 
entire breadth of the strobile (Fig. 78). In the posterior segments the 
reproductive apertures are near the margin. One of the specimens 
with segments thus characterized had the following dimensions: 
Length 33 millimeters; greatest breadth 0.7 millimeter, at which point 
the length of segments was 0.1 millimeter; length of posterior segments 
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