The Hirudinea of Illinois. 537 



a single large crescentic one, into the deep ends of which the 

 prostate cornua open. 



The female organs present no important differential char- 

 acters, although the ovaries (ov) of all of the specimens dis- 

 sected reached to ganglion XYIII. 



Color. — Living specimens, according to Verrill's description 

 and a water-color sketch sent me by Professor Eeighard, are 

 pale red with some darker cloudings. 



Preserved specimens may be separated into two groups 

 according to the amount of pigment present. One group, 

 which includes the smaller and a portion of the larger ones, 

 lacks pigment entirely ; the other, which includes most of the 

 larger examples, has the dorsal surface marked with more or 

 less numerous minute black flecks which differ greatly in 

 number and somewhat in arrangement. Many specimens 

 have so little pigment as to appear light-colored, with a faint 

 dark band on either side of a median clear band ; in others 

 the dark bands are very broad ; and still others appear quite 

 dark, the pigment specks being very numerous and close and 

 extending continuously over the median region. In all cases 

 the margins, including the region of the lateral vessels, are 

 unpigmented ; and in no case does the pigment assume any 

 other form than that of minute flecks more or less closely 

 placed. 



Dina microstoma sp. nov. 



Diagnosis. — Complete ' somites quinqueannulate, b 6 en- 

 larged and subdivided ; first pair of eyes in III ; male orifice 

 at XII b 2/ a 2, female orifice at XII/XIII ; median chamber of 

 atrium relatively large and without median groove ; prostate 

 cornua inconspicuous, shorter than diameter of median 

 chamber ; vasa deferentia lacking anterior loop and ending 

 abruptly at the atrium. 



General Description. — This is a generally slender species. 

 Well-preserved specimens are nearly terete and in extension 

 linear. An average specimen measures : — 



