The Hirudinea of Illinois. 497 



pounded of narrow brown lines, the number of which varies 

 according to the width of the stripe. The longitudinal stripes 

 correspond with the arrangement of the musculature as 

 described for other species by Graf ('99). On many speci- 

 mens these stripes are more or less interrupted on «2 of each 

 somite by transverse whitish spots which occur almost con- 

 stantly in two, four, or six longitudinal series, of which the 

 most constant lie just external to the dorso-lateral papilla?, 

 the next on the flanks of the median papilla?, and the third 

 near the margins. The extreme of this arrangement results 

 in a handsome metameric pattern in which a 2 becomes con- 

 spicuously marked by a row of white spots which on the 

 posterior somites unite to form a band. In such specimens 

 the ground color becomes a pale brown marked by numerous 

 narrow dark brown or almost black lines, of which a pair 

 near the middle line are very conspicuous. The white spots 

 are least developed anteriorly, but become more extensive 

 and closer together posteriorly. Individuals differ greatly as 

 to the exact manner and extent of the complementary develop- 

 ment of light and dark elements in the pattern. The entire 

 preocular region is beautifully white, while brown rays on a 

 white ground mark the sucker. 



Habits. — In habits G. lineata resembles G. complanata, with 

 which it is frequently found. Probably this species inhabits 

 colder brooks than any other of our glossiphonids. 



Glossiphonia stagnalis (Linn^us). 



Hirudo stagnalis Linnaeus (1758). 

 Hirudo bioculata Bergmann (1757). 

 Clepsine modesta Verrill ('74). 



Diagnosis. — Somites I to III included in preocular region ; 

 single pair of eyes on anterior annulus of IV, which is 

 obscurely biannulate ; V biannulate ; VI to XXIV triannu- 

 late ; XXV and XXVI biannulate, the latter somewhat united 

 to XXVII ; genital orifices as in G. lineata ; a dorsal chitinoid 

 glandular bursa situated at VIII a 1/a 2 ; gastric cseca small, 

 simple, variable, never more than six pairs, of which any or 

 all of the first three may be absent ; size small and form con- 



