KEY TO THE SPECIES DESCRIBED IN THIS PAPER 



The bold-faced numbers refer to the page. 



I. Mouth a small pore-like opening in the disk of the anterior 

 sucker, through which a muscular pharyngeal proboscis may 

 be protruded. 

 A. Complete somites formed of three annuli. 



a. Genital orifices separated by a single annulus ; eyes one 

 pair, distinct, 

 b. A dark brown cuticular plate and underlying gland 

 on the dorsum of somite VIII. 



1. Body capable of great extension; color pale — - 



pink, gray or brownish. 



Glossiphonia stagnalis, 77 

 bb. No nuchal plate or gland in the adult. 



2. Body very slender, elongated and little flat- 



tened ; very transparent owing to the nearly 

 complete absence of pigment ; no cutaneous 

 papillae. Glossiphonia nepheloidea, 76 



3. Body relatively broad and flat ; more or less 



heavily pigmented with brown arranged in 

 linear pattern, annulus a2 marked by white 

 spots usually arranged in transverse rows ; 

 three longitudinal series of conspicuous black 

 papillae. Glossiphonia fusca, 80 



aa. Genital orifices separated by two annuli ; eyes in sev- 

 eral pairs. 



4. Three pairs of eyes ; gastric caeca six or seven 



pairs; a pair of dark longitudinal lines both 

 above and below. 



Glossiphonia complanata, 82 



5. Four pairs of sub-equal eyes, all simple; gastric 



caeca nine pairs. Hemiclepsis occidentalis, 96 



6. One pair of compound eyes followed by three 



or more pairs of much smaller simple eyes ; 

 gastric caeca seven pairs. 



Plocabdello hollensis, 94 



