586 
Cestodes from Selachians 
large and elongate oval, each measuring 1-1 x 0-6 mm., divided into 
three unequal loculi by two transverse costae. The anterior loculus 
is the largest and at its anterior corner two pairs of hooks are present. 
Hooks thorn-like, strongly curved, measuring 0-4 x 0-5 mm. (basal 
width), the pair on the same side of the bothridium are connected by 
hbrous tissue. In front of hooks, bothridium carries a pad with 
three accessory suckers. Neck varies in length according to state of 
contraction, measuring T3—T5 x 0-8 mm. (average width). 
The strobila of the largest specimen is widest (4-5 mm.) near the 
posterior end, narrowest (0-8 mm.) at the neck, the last segment 
measuring 1-5—2-0 mm. in breadth. The strobila is nearly of uniform 
thickness (1-0 mm. or more) excepting at the posterior part of the body 
which is nodularly swollen by the distended uterus (fig. 3, E and F). 
The segments increase gradually in length toward the posterior 
end, the anterior segment measures 0-2 mm., the middle 0-5 mm. 
and the posterior TO mm. long. The segments also increase in breadth 
posteriorly to near the end of the body where they again narrow at 
the very end. The posterior segmental border is angular or laciniated 
by emarginations as shown in the accompanying figures; the lacinia- 
tion differs slightly in different parts of body; the emarginations of the 
posterior border are generally four in number, two on the dorsal and 
ventral median lines and one on each side of segment. The posterior 
border overlaps the next following segment so as to give a serrated 
appearance to the worm. Serration, emargination or laciniation are 
conspicuous in the anterior half or more of the worm and are obliterated 
in the rest of the strobila. 
Genital pores irregularly alternate, situated in front of the middle 
of the lateral margin. Uterine openings placed on median line of 
the flat surface. 
Excretory system. Dorsal canals very small, the ventral larger, 
measuring 0-046 x 0-034 mm. Wall of ventral canal well developed, 
0-005 mm. in thickness. Transverse commissures of ventral canals 
absent. 
Musculature. Large longitudinal muscle bundles (ca. 100) are some¬ 
what regularly arranged all around the median field. The anterior 
portion of body is furnished with fewer muscle bundles, but they are 
well developed (each bundle measuring 0-041 mm. in long and 0-02— 
0-03 mm. in short diameter). 
Male organs. Cirrus pouch (PI. XXIII, fig. 21, B) oval, 0-28 x 
0-17 mm., surrounded by a thin muscular wall; its cavity is occupied 
