The Hirudinea of Illinois. 505 



the conspicuous sucker, and gently tapering anteriorly to the 

 broadly rounded upper lip. Depressed throughout, with the 

 dorsum convex and venter flat ; the margins somewhat sharp. 



There is no expanded anterior sucker (PI. XLIII., Fig. 8) 

 or head as in typical ichthyobdellids, but this end of the body 

 is formed like a glossiphonid or, excepting the character of 

 the mouth, more like a nephelid. The lip is broad and 

 rounded and in this example is turned in ventralward. On 

 the dorsal side it is divided into annuli as described under 

 the caption Annuli and Somites. The ventral surface pre- 

 sents a very deep cavity from out of which rises a prominent 

 rounded elevation, near the summit of which the pore-like 

 mouth is situated. The posterior boundary of the sucker is 

 formed by somite V. No pigmented eyes can be detected, but 

 an opaque spot on the third and fourth rings may possibly be 

 eyes, though appearing more like a gland. 



No clitellum is developed. The male genital orifice (PI. 

 XLIII., Fig. 8, cf) is a minute pore situated in a transversely 

 extended elliptical disc at XI/XII ; but on the ventral side 

 the annuli XII 6 1 and b 2 are obsolete and the male 

 disc therefore somewhat overspreads annulus b 3. The female 

 pore (?) is in the form of a small transverse slit in annulus 

 XII 1)4 and, owing to the great reduction of b 1 and 6 2, 

 appears to be separated from the male opening by only one 

 and one half annuli. 



Most remarkable of all of the external features of this 

 leech is the posterior sucker (PI. XLIII., Fig. 8-10). It is 

 much wider than any part of the body, of hemispherical 

 form, largely free on all sides, and supported by a narrow 

 central pedicle. The ventral surface (PL XLIII., Fig. 10) is 

 very deeply cupped, and in the specimen described the rim is 

 somewhat contracted, making the diameter of the opening 

 somewhat less than that of the internal cavity. From the 

 inner face of the sucker, a short distance back from the sharp 

 margin, spring about thirty (exactly thirty in this example) 

 slender finger-like processes, which project more or less 

 freely into the cavity. Owing to their contractile nature 

 they may vary in length and diameter, but when extended 



