CASTLE: NORTH AMERICAN RHYNCHOBDELLID A. 21 
4, Eyes six, the first pair small and close together, the others 
farther apart; rings without metameric markings, or with dark 
pigment on the anterior ring of each somite. 
G. heteroclita (p. 42) 
C. Crop diverticula seven pairs ; male and female genital pores separated 
by two body rings. 
5. Hyes six, distinct, in two parallel rows; a conspicuous longi- 
tudinal band of dark pigment on either side of the median plane 
dorsally, and a fainter one Salar: ; mMeconspicuous papille on 
the dorsal surface . . . - - « + G. elegans (p. 46) 
6. Eyes apparently a Avale pair, far forward on the head and 
confluent ; back distinctly papillose. A large species, often found 
ouiturtles 5°, . - - - - « - - «  G. parasitica (p. 51) 
IV. DESCRIPTION OF SPECIES. 
1. Glossiphonia stagnalis Liynaus (1758). 
Plate 1, Figs. 1, 3; Plate 2, Fig. 4; Plate 3, Figs. 7-10, 12; Plate 8, Fig. 34. 
Hirudo stagnalis Linneus (1758); H. bioculata O. F. Miiller (1774); Clepsine 
bioculata Savigny (’20); C. modesta Verrill ("72); C. submodesta Nichol- 
son (’73). 
a. Hasitat, Form, Sizp, Conor. 
This species is found in Kurope, the adjacent parts of Asia and Africa, and 
in North and South America. As one might expect in the case of so cosmo- 
politan a form, much has been written about it, but its external morphology 
has never been carefully and accurately analyzed, and published accounts of its 
internal anatomy contain a number of errors or omissions, some of which | 
hope to rectify. 
The general form of the body as seen in dorsal view, when partially extended, 
is shown in Figures 1 and 4. The body is broadest posterior to its middle and 
thence tapers gradually toward both ends. The head, which is only slightly 
wider than the neck, is evenly rounded in front (Figure 3) ; dorso-ventrally 
the body is very much flattened, especially when at rest. The animal is very 
active in its movements and can greatly elongate its body so as to become more 
than ten times as long as it is broad. The largest individuals measure as 
follows : — 
Length, fully extended, 20-25 mm. ; at rest, 8-10 mm. 
Width, fully extended, about 2 mm.; at rest, about 5 mm. 
Color, flesh-color or grayish. Small individuals are usually quite clear and 
transparent, but larger ones are apt to be more or less opaque. This opacity, 
