494 Illinois State Laboratory of Natural History. 



series, of which the median is the best developed ; epididymis 

 forming a loop which reaches into somite XV. 



General Description. — A small species seldom over half 

 an inch in length, but capable of moderate extension. In 

 the resting state broad and slightly convex above but not 

 foliaceous, the body being rather thick ; when extended, 

 strongly convex. 



The anterior sucker is of moderate size and has a rather 

 thick margin into which the annulations extend. It is deeply 

 concave and presents no central elevation. The mouth is 

 large and situated just behind the anterior rim of the sucker, 

 apparently in somite II. Occasionally it is succeeded by a 

 transverse fold. The eyes, of which there is a single pair, 

 are of remarkable size, their diameter being nearly equal 

 to the length of annulus IV {a 1+a 2) in which they lie. They 

 are simple and correspond to the second pair of G. complanata. 

 The genital pores are separated by but a single annulus, the 

 neural annulus of -somite XII ; they consequently both lie 

 within the limits of that somite. 



The posterior sucker is large but relatively little exposed, 

 elliptical in form, and with a thick margin. It reaches for- 

 ward to XXIII a 2. 



Annuli and Somites (PL XLIL, Fig. 6). — I and II are 

 uniannulate and constitute the undivided anterior lobe. 



III is biannulate, the anterior ring being somewhat the 

 larger. No sensillre are visible in surface views, but sections 

 show that the eyes are derived from this somite. 



IV is biannulate, but the anterior annulus is relatively larger 

 and is faintly subdivided; it bears the very conspicuous pair 

 of eyes. At the margin this somite becomes uniannulate 

 and forms the posterior rim of the sucker. 



V is triannulate above. y!2 is much longer than a 1, 

 especially mesially, where it appears to be almost subdivided. 

 The furrow a 2/a 3 is the deepest in this neighborhood and 

 defines the posterior limits of the head very sharply. Ven- 

 trally a 1 and a 2 unite while a 3, as usual, remains distinct. 



VI is the first of the fully triannulate somites, and all three 

 annuli are distinct ventrally as well as dorsally. In all of the 



