The lllradiuca of Illinois. 503 



distinct to XXV, on which latter they approach very close to 

 the dorso-laterals. By the fusion of the sensillfe of these two 

 series on XXVI and XXVII but three pairs remain. Very 

 minute supra-marginals {sni) are also present on most of the 

 annuli. Near the margin of the sucker one or two very 

 regular circles of eight sensilhie are ranged. 



Reproductive Organs. — The six pairs of testes are in the 

 anterior ends of somites XIV to XIX, extending somewhat 

 into the preceding somites. The enlarged region of the 

 sperm- duct (epididymis and ductus ejaculatorius) forms a 

 coil or two, and its full length when extended laterally 

 scarcely reaches to the margin of the body at the male pore. 

 The prostate cornua are short and wide. The anterior and 

 dorsal lobe of the ovary, which represents the closed end of 

 the sac, is large and prominently projecting. 



Alimentary Canal. — Pharynx slender and very extensible, 

 its glands small. The same number and general arrangement 

 of the gastric cteca as in P. parasitica are found in this species, 

 but they are much less subdivided and branched. 



Color. — The colors of this species are generally dull and 

 uniform. Very commonly the entire body is a light or darker 

 green or brownish green with a few flecks or lines of deep 

 green and an obscure pale yellow border. Sometimes the 

 pattern is more definite, as in the following case : The entire 

 central region of the dorsum is of a brownish green color 

 which on the neural annuli extends to the margins in the 

 form of narrow sharp-pointed projections, by which a series 

 of large yellow marginal spots are separated from one another 

 and thus barely escape forming a continuous yellow border. 

 Six or seven elongated light yellow spots form a median series 

 and alternate with short dark greenish brown longitudinal 

 lines. Smaller, more or less confluent light yellow spots mark 

 the lateral carinte. The head is marked by an irregular green- 

 edged dark brown "spread eagle" figure, which leaves a large 

 anterior and a pair of posterior lateral light spots. 



Habits. — This species to a great degree lacks the social 

 instincts of most glossiphonids. A far larger number of 

 specimens are found singly than in company. In the neigh- 



