Lake Maxinkuckee, Physical and Biological Survey 89 



North American Fresh-water RhynchobdellidaB, Bulletin Museum 

 of Comparative Zoology, Vol. XXXVI (1901), pp. 16-64; Moore, 

 The Hirudinea of Illinois, Bulletin Illinois State Laboratory of 

 Natural History, Vol. V (1901), pp. 479-547; Nachtrieb, Heming- 

 way & Moore, The Leeches of Minnesota, Geological and Natural 

 History Survey of Minnesota, Zoological Series, No. V, 1912, es- 

 pecially Part III, Classification of the Leeches of Minnesota. 



For the determination of the species herein listed the following 

 Key will serve: 



A. Mouth a small pore through which the slender exertile pharyngeal pro- 

 boscis may be protruded; complete somites usually composed of three 

 rings, one or more of which may be partially subdivided. Glossiphonidse 



B. Eyes all simple, one to three pairs, those of the two sides usually dis- 

 tinct; form slightly or moderately depressed; cutaneous papillae few and 

 mostly small or obsolete; gastric caeca small and simple or little branched, 

 sometimes reduced or absent; no compact pharyngeal glands. 



Glossiphonia 



C. Eyes one pair, widely separated; genital orifices separated by one an- 

 nulus; gastric caeca more or less reduced, size small. (Subgenus Helob- 

 della. ) 



1. A brown or yellow cuticular nuchal plate and underlying gland on 

 dorsum of somite VII; color pale pink, gray, brownish or greenish; 

 gastric caeca three to six pairs, the first two or three pairs always 

 small; usual length 10 to 15 mm.; slender. G. stagnalis 



2. No nuchal plate or gland in adult; more or less heavily pigmented 

 with brown in longitudinal lines with metameric white spots on middle 

 annulus of complete segments; generally three longitudinal series of 

 papillae conspicuously pigmented with dark brown or black; gastric 

 caeca five or six pairs ; length of G. stagnalis but stouter and more 

 depressed. G. fusca 



CC. Eyes three pairs; genital orifices separated by two annuli; gastric caeca 

 not reduced, six or seven pairs. (Glossiphonia ss:) 



3. Eyes in regular longitudinal series; a pair of dark longitudinal para- 

 median lines above and below; opaque; length 15 to 25 mm.; robust. 



G. complanata 



4. Eyes grouped in twos at the angles of a triangle; translucent and 

 little pigmented, no dark longitudinal lines; length 6 to 12 mm.; 

 broadest and most depressed of genus. G. heteroclita 



BB. A single pair of compound eyes, often united into a common pigment 

 mass and rarely followed by several pairs of simple eyes; form moder- 

 ately or greatly depressed; cutaneous papillae usually numerous and con- 

 spicuous; gastric caeca seven pairs, large and more or less complexly 

 branched; a pair of compact pharyngeal glands in addition to the dif- 

 fuse salivary glands. Placobdella 



D. Somites I-V much widened to form a distinct head; form little depressed. 



5. Dorsum bearing three prominent papillated keels; color usually green 

 or olive; length rarely exceeds 20 mm. P. montifera 



