PARASITES FROM THE SOCIETY'S GARDENS. 149 
somewhat flat species, with a pronounced cervical concavity. As 
in many other species of the genus, the head has a tendency to 
be bent sharply on to the ventral surface of the body. 
The specimens measured 2°9-6°3 mm. in length. One, 4°6 mm. 
in length, was immature, but another, of 5:6 mm. in length, was 
full of ova, so that the maturity len ath is probably about 5 mm. 
The areatest breadth, across the nee sucker, is about one-fifth 
of the length. Behind the ventral sucker the breadth is fairly 
uniform, but the tail is distinctly pointed. The breadth across 
the head is about one-tenth of the body-length. 
There are 35 cephalic spines, arranged in the typical fashion in 
two uninterrupted rows, with a group of five terminal spines at 
each end. In the anterior row the spines are slightly shorter than 
in the posterior row, the average size being ‘(099 mm. and:103 mm. 
respectively. The terminal spines are slightly smaller, measuring 
"093 mm. The shortest spine on either side is the superficial 
spine third from the inner end of the terminal group. In the 
only specimen in which its dimensions could be accurately 
determined, it measured ‘091 mm. on the right side and only 
078 mm. on the left. The cephalic spines present two peculi- 
arities which have not apparently been observed in any hitherto 
described species of Hchinostomum. In the first place their shape 
is unusual. Instead of the common symmetrical peg-shape, their 
distal end is inflated in the form of a somewhat triangular knob, 
which is slightly sculptured. ‘The knob is situated on the upper 
surface of the spine, and comprises about one-third of its total 
length. An idea of its shape will best be gathered from reference 
to fig. 9a. There is the further peculiarity that each spine is 
connected to the edge of the cephalic dise by a thin web-like 
membrane which is joined to the spine along pretty nearly its 
whole length. 
The whole of the neck, both dorsally and ventrally, is covered 
with stout cuticular spines, but these do not extend very far 
beyond the ventral sucker. 
In a 5-6 mm. specimen the large oral sucker measures *22 mm. 
in diameter, and the ventral sucker °72 mm. The latter is usually 
globular, but in one case it was somewhat deepened. It lies 
at a distance of 1°43 mm. from the anterior end. The neck is 
thus a little more than one-fourth of the body-length. There 
is a short prepharynx about -06 mm. in length, followed by 
a pharvnx measuring °19x-13 mm. The cesophagus is about 
*46 mm. in length, and the bifurcation occurs just in front of 
the ventral sucker. The diverticula are somewhat crenated, and 
extend right to the posterior end of the body. 
The genital aperture lies in the middle line just over the 
intestinal bifurcation. The cirrus-pouch is small and stout, and 
overlaps the ventral sucker only to a slight extent. Its dimensions 
are 45 x °18 mm., and it encloses a convoluted vesicula seminalis, 
a short pars prostatica, and a twisted ductus and cirrus. The 
testes are rather small and of irregular contour, there being 
