The Hirudinea of Illinois. 539 



The male gonopore is situated as usual at XII £2/# 2, the 

 female at XII/XIII, three annuli consequently intervening. 

 The former is a large and conspicuous opening usually sur- 

 rounded by a thin integumental disc which spreads over 

 about one half of the contiguous annuli. The female pore is 

 small and usually concealed. A strongly developed clitellum 

 is generally present. It is thick both dorsally and ventrally, 

 sharply defined, and extends over fifteen annuli, from X b 5 

 to XIII bl. The nephridiopores are as usual. 



Even for a nephelid the posterior sucker is weak and small. 

 It is very broadly attached, with scarcely any free margin 

 anteriorly, where it reaches only as far forward as XXVI. 

 Eight low radiating ridges or lines of papillae disposed in 

 pairs mark its upper surface. Anus large, with a much 

 wrinkled margin, XXYI/XXYII. 



Annuli and Somites. — The external features of metamerism 

 in this species differ but little from those of E. punctata, 

 but as Bristol has adopted another standard of enumera- 

 tion in his description of that species it seems best to give a 

 brief account of the present species. 



I is the wide anterior region of the lip. 



II is a narrow preocular annulus bearing one row of sen- 

 sory papilla?. 



III is a single wide annulus faintly subdivided and bearing 

 a complete row of sense organs posteriorly and an incomplete 

 row anteriorly. The large pair of eyes are on its extreme 

 anterior part and are separated by a distance of about three 

 times their width. 



IV is biannulate, the first ring being distinctly subdivided 

 and separated from the second dorsally but united to it ven- 

 trally. In many cases its posterior furrow is very deep and 

 limits the head region as noted above. The second group of 

 eyes is borne by this somite, the ventral pair being on the 

 furrow a 2Ja 3, the dorsal just in advance of it. 



V is also biannulate, the first annulus bearing two rows of 

 sense organs and being somewhat wider than the second. 



VI is triannulate. A 1 and a 3 are each slightly wider than 



