378 PROCEEDINGS OF THE ACADEMY OF [May, 



Casco Bay and northward in Maine, where it occurs under stones and 

 among grass roots up to high-water mark on muddy and gravelly 

 shores. While apparently less plentiful south of Cape Cod, it is com- 

 mon at many suitable points on the shores of Vineyard Sound, Buz- 

 zard's Bay, Narragansett Bay and Long Island Sound. 



Without being able to decide the matter definitely, it seems ex- 

 tremely probable that this is the species described by Leidy. Although 

 the characters given in the brief description of L. tenuis are not diag- 

 nostic, they are sufficient to eliminate every other species described in 

 this paper except the brackish w^ater Limnodrilus suhsalsus, while they 

 all and the character of the habitat, as well, apply to C. arenarius. 

 Vaillant, indeed, has already referred Lumhriculus tenuis doubtfully 

 to Clitellio. Later writers have been more cautious. 



In Prof. Verrill's collections this species occurs far more frequently 

 than any other and usually under the name of Clitellio irrorata, thus 

 giving the best of authority for the inclusion of the latter in the syn- 

 onymy. It is this species that is figured under the name of C. irrorata 

 in Trans. Conn. Acad., 1881, PI. VIII, figs. 3 and 3a. The localities 

 represented cover a wide extent of coast and, named from north south- 

 ward, are as follows: Nova Scotia, Bay of Fundy, Casco Bay, Cape 

 Ann, Gloucester, Massachusetts; Salem, Massachusetts; Cape Cod, 

 Vineyard Sound, Wood's Hole and New Haven. 

 Monopylephorus glaber sp. nov. Plate XXXII, figs. 1-6. 



This species is relatively short and stout for a tubificid, the largest 

 examples not exceeding 40 mm., and the usual length of living mature 

 worms being about 25-30 mm., wuth a diameter of .8 mm. Young 

 examples are relatively much more slender. In mature worms there 

 are from 67-74 segments, and generally they are 4-ringed, bearing the 

 setge on the third and consequently well behind the middle. The 

 greatest diameter is at the clitellum and genital region, from w^hich the 

 body tapers rapidly to the small pointed prostomium and very gently 

 to the anal somite. The clitellum occupies part of X, all of XI and 

 XII, and sometimes extends on to XIII. Except for the sensory hairs 

 belonging to a zone of cutaneous organs encircling the middle of each 

 somite, the skin is devoid of cuticular pilosities and perfectly smooth. 

 Owing in part to the presence of grayish-brown pigment granules, and 

 in part to the remarkably high peritoneal layer of cells, the body walls 

 are decidedly opaque. The external opening of the genital bursa is a 

 conspicuous median, transversely elongated aperture in the setae zone 

 on the venter of XI. The female pores are paired in the furrow 



