200 Field Columbian Museum — Zoology, Vol. VII. 



in cross-section elliptical in post-clitellar part; lateral margins 

 rounded except near the caudal sucker, where thin lateral wings 

 extend for a short distance. 



Mouth moderate, the upper lip rather short and broad and 

 moderately furrowed. Eyes 3 pairs, the first much the largest 

 and most conspicuous, situated in the dorsum of somite II, the 

 other two pairs equal and situated one above the other at the sides 

 of the mouth on somite IV. Clitellum thick, completely zonular, 

 extending over 15 annuli (Xb^ to XIII b * inclusive), well defined 

 and broader than contiguous segments. Genital orifices separated 

 by three full annuli, the male being situated between the second and 

 third rings of somite XII (XII b Va ^) , the female at XII/XIII. On 

 mature worms the male orifice is prominent, with rugose margins 

 and elevated on a broad conical papilla. When the atrial chamber 

 is everted this region appears as a slightly elliptical disk with the 

 longer diameter transverse, with a slightly raised marginal rim, 

 and near the center two small openings of the prostate horns. 

 Completely quinque-annulate somites have all annuli of equal 

 length, and not further subdivided except on much contracted 

 specimens, which have all rings equally subdivided by transverse 

 furrows across the middle. Anus large, with radical furrows sur- 

 rounding it, situated 3 annuli in front of the anus. Posterior suck- 

 er thin, flat, its diameter about two-thirds the greatest width 

 of the body, marked on each side by several raised radiating 

 lines. 



Color, yellowish olive or dull green, marked for the entire 

 length with four longitudinal stripes composed of numerous small 

 black spots with pale centers in which sensory papillae are situ- 

 ated. The middle (paramedian) pair is usually the darker, and 

 the supra-marginal duller and more diffuse, while the median 

 light area is paler than those between the two pairs of dark stripes. 

 Ventral surface and lateral margins plain gray or ashy and quite 

 unpigmented. Other specimens have the dorsal pigmentation 

 diffuse, giving an effect of dull brown or brownish black, the 

 paramedian region being always deepest. In such specimens, 

 the furrows are always pale, and the rings speckled with small 

 white spots indicating the position of the sense organs. 



Atrium with median chamber relatively spacious, much as in 

 Dina microstoma, not deeply bilobed nor much incised by the 

 nerve cord ; prostate cornua small, curved laterally and downward 

 to meet the vasa deferentia, which pass forward as long loops as 

 far as ganglion XI. 



