The Hirudinea of Illinois. 519 



i 



HiEMOPIS Savigny. 

 Hsemopis marmoratis (Say). 



Hirudo marmorata Say ("24). 

 Aulastomum lacustre Leidy ('68). 



Diagnosis. — Amrali VII b5 and b 6 and VIII b\ and £2 

 indicated on the enlarged primary annuli but not fully devel- 

 oped ; d pore on 32 (XI b 6) or 31/32 (XI b5/b6), ? pore 

 on 37 (XII £6) or 36/37 (XII bojb6); atrium and vagina 

 reaching into somite XVII; ovaries just behind ganglion 

 XIV. 



General Description. — This species reaches a greater size 

 than is attained by any of the Illinois examples, the largest 

 of which measures : — 



mm. 



Total length, 104. 



Length to cT pore, . . . . . . .22. 



Greatest width, (XVII), 15.5 



Width at d pore, 12. 



" " anus, 7.7 



Depth at XVII, 6.5 



" " c? pore, 3.8 



" " anus, . . . . . . .2.5 



Diameter of posterior sucker, . . . . 6.5 



Owing to the great development of botryoidal tissue the 

 body is exceedingly soft and consequently varies greatly in 

 shape, when alive, according to the various states of rest and 

 activity, in preserved specimens, as a result of the different 

 methods adopted for fixation and preservation; When 

 actively swimming, and especially when the stomach is 

 empty, the body is elongated and flattened but never very 

 slender. (This is yearly the condition of the example meas- 

 ured.) The width is generally greatest at about the middle 

 of the body, but differs very little between the clitellum and 

 the last complete somite. In preserved specimens the clitel- 

 lum is frequently the widest part of the body. Anterior to 

 the clitellum the body tapers rapidly to the broadly rounded 



