512 Illinois State Laboratory of Natural History. 



General Description. — The largest extended specimen has 



the following measurements : — 



mm. 

 Total length, . . . . . . . .84. 



Length to male pore, . . . . . . 19. 



Greatest width (about XX), . . . . .7.8 



Width at male pore, . . . . . . 7 . 



Width at anus, . . . . . . 3 . 



Depth at XX, . . . . . . . 2.5 



Depth at male pore, . . . . . .2.8 



Depth at anus, . . . . . . . 1.5 



Diameter of posterior sucker, . . . . .4.3 



This is a very pretty leech of moderate size and slender 

 graceful form. The preserved specimens are depressed 

 throughout, except just posterior to the mouth, the ventral 

 surface is flat, the dorsal gently convex, with an evident 

 tendency to rise to a rounded median ridge. In some exam- 

 ples the middle two thirds, or so, of the body remains of 

 nearly uniform width; in others the outline tapers gently and 

 regularly from the place of greatest width forward to the 

 mouth. 



Probably the body of the living leech has a texture about 

 like Htsmopis lateralis, as the muscles and botryoidal tissue 

 display a similar relative degree of development. Except for 

 a few wrinkles and the very slightly elevated sensitise the 

 surface is quite smooth. 



All of the annuli are clearly marked by smooth even fur- 

 rows, but owing to the absence of any well-marked transverse 

 ridges they are not angulated and the margins of the body do 

 not appear denticulate. Most of the annuli, however, do 

 show a faint incipient transverse furrow, dividing them into 

 approximately equal halves, the posterior one of which may 

 be marked by a very faint raised line. 



As in Hirudo, but unlike Hcemopis, there is a distinct very 

 narrow unsegmented margin or border to the anterior sucker 

 (PI. XLIV., Fig. 13), which is separated on the ventral side 

 by a shallow trench from the actual mouth rim. The mouth 

 and sucker are small. A median sulcus divides the ventral 



