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THE LEECHES OF MINNESOTA 



aaa. Genital orifices separated by two annuli; a single pair 

 of compound eyes; gastric caeca, seven pairs, 

 branched, 

 b. Somites I to V much widened to form a distinct 

 head. 



7. Somites I and II biannulate ; the dorsum marked 



by three strong papillated keels ; gastric caeca 

 much branched. Placobdella montifera, 88 

 bb. Anterior somites not especially widened. 



c. Posterior sucker very free and supported on a 

 slender peduncle; anus at XXIII/XXIV; 

 gastric cseca little branched. 



8. Body rather high, very contractile ; dorsal papil- 



lae wanting. Placobdella pediculata, 90 



cc. Posterior sucker not supported on a specially 

 slender peduncle ; anus at XXVII/XXVIII ; 

 gastric cseca much branched. 



9. Body very much depressed ; dorsal papillae few, 



low and smooth ; integuments rather opaque. 

 Placobdella parasitica, 84 



10. Body very much depressed; dorsal papillae 



numerous, rough and usually high ; integu- 

 ments translucent. Placobdella rugosa, 86 

 AA. Complete somites composed of more than three annuli. 



11. Complete somites consisting of six unequal 



annuli ; posterior sucker very large and pro- 

 vided with a marginal circle of contractile 

 papillae ; eyes one pair contiguous in middle 

 line. Actinobdella inequiannulata, 99 



12. Complete somites consisting of twelve or four- 



teen approximately equal annuli ; body divid- 

 ed into two regions ; posterior sucker without 

 marginal papillae ; eyes widely separated on 

 posterior part of head. 



Piscicola punctata, 103 



II. Mouth large, the sucker appearing as its bounding lips ; the 



pharynx not forming a protrusible proboscis. 



A. Eyes five pairs, arranged in a regular arch on somites IT to 



VI; genital ducts with complex copulatory apparatus: 



testes strictly paired, their number moderate ; at least 



one pair of gastric caeca present. 



