CASTLE: NORTH AMERICAN RHYNCHOBDELLID, 39 
as seen in a lateral view is shown in Figure 14, cb. It lies for the most part 
in somites vit. and v1. This is about a somite posterior to the usual position 
of the brain in G. stagnalis (Figures 4, 7). 
The number of fused ganglia represented in the brain is, as in G. stagnalis, 
six, and the nerve capsules have the same general arrangement as in that 
species. The yentral capsules of neuromeres I1.—v. are placed side by side, 
while those of neuromere VI. lie one behind the other (Figure 18 ; compare 
Figure 10, Plate 3). The six capsules of neuromere I. are situated well dorsal, 
as in G. stagnalis, and the supra-cesophageal connective is pushed back nearly 
over the middle of the entire brain mass (Figures 14, 16). The lateral cap- 
sules of neuromere II. are shown in the dorsal view (Figure 16) ; those of neu- 
romeres III.-VI., in the ventral view (Figure 18). 
In Figure 14, which represents a parasagittal section, is shown the position 
of the paramedian sensille of the head somites, certain of which also appear 
in Figure 15. These indicate clearly the sensory rings of the somites in that 
region, and so aid in the determination of the external limits of the somites, 
The eye is clearly derived from one of the segmental organs of somite I. 
(ring 2), as the position of its nerve indicates. This view is confirmed by a 
comparison with the conditions existing in G. heteroclita and G. elegans. 
8. Glossiphonia elongata sp. nov. 
Plate 6. 
a. Hasitat, Form, Size, Cotor. 
This leech first came to my notice in September, 1898. While collecting 
G. stagnalis from Spy Pond, near Cambridge, I found three or four leeches 
which, although of about the same size as stagnalis and occurring in similar 
situations, at once attracted my attention because of their more slender bodies 
and the peculiarities of their movements. These animals were carefully pre- 
served, and diligent search was made the following spring for more. This 
search, however, was fruitless ; but in September, 1899, I was fortunate enough 
to find quite a number of individuals in a pool near Fresh Pond, Cambridge, 
some of which I have since kept alive in aquaria for several months. 
The body is less flattened dorso-ventrally in this species than in any other 
Glossiphonia known to me, being sub-cylindrical in cross-section. It is ex- 
tremely slender, even when contracted, and both head and acetabulum are 
small (Figure 27, Plate 6). This species does not roll itself into a ball, as 
other species do, when disturbed. Instead, it writhes about or twists itself 
into knots like an earthworm. In aquaria it moves little from place to place, 
but, attached by its weak posterior sucker, extends its snake-like body searching 
hither and thither as for a place of concealment, or, losing its attachment, seems 
unable to regain it and writhes helplessly like an earthworm on a smooth 
surface. 
The largest individuals which I have examined measure as follows : — 
