392 PROCEEDINGS OF THE ACADEMY OF [May, 



present, though several of the spermatheca? contained small elongated 

 aggregations of spermatozoa. 



Nephridia are present on the left side only of most, if not of all, seg- 

 ments. In sections they are very conspicuous owing to the large size 

 especially of the middle tubule loop, but they are not sufficiently well 

 preserved to permit a detailed description of their structure. The 

 terminal vesicles are likewise large and the external pores, which are 

 situated well mediad and a little cephalad of the ventral setae, are 

 very conspicuous in entire mounts, in which their asymmetry is very 

 striking. 



The brain (fig. 12) is somewhat broader than long, slightly cleft ante- 

 riorly and deeply cleft posteriorly. 



This species has been found only under stones between tides on the 

 shores of the Acushnet river, above New Bedford, Massachusetts. 

 At this point the water is brackish. 

 Limnodrilus subsalsus sp. nov. PI. XXXIII, figs. 19-22. 



Length up to 40 mm., but most examples are less than this; greatest 

 diameter (at XII) .6 mm. ; number of segments up to 12G. 



The prostomium is conical with the apex rounded, one and one-half 

 times to twice as long as broad. The first two or three segments are 

 very short, not exceeding the prostomium ; succeeding somites rapidly 

 increase in length to X, which, with those following, is five or six times 

 that length. The greatest diameter is at XI and XII, from which point 

 it decreases to the very slender posterior third. Usually the peristo- 

 mium is simple, but occasionally is faintly biannulate; II, III and IV 

 are very distinctly biannulate, with a small, sharply defined annulus 

 split off anterior to the setse, which are borne on the prominent middle 

 portion of the larger annulus; V is triannulate with the setse posterior 

 to the middle of the largest, middle annulus ; VI has a second narrow 

 annulus splitting off anterior to the setigerous one and a single one be- 

 hind; VII is more distinctly quadriannulate, and VIII has four narrow 

 annuli before and two behind the large setigerous one. The next few 

 annuli present an irregular multiannulate condition, there being in 

 most cases 5 presetal and 2 postsetal rings, which are nearly or quite 

 equal to the setigerous one. Postclitellar somites are only very ob- 

 scurely or not at all annulated. 



Setae are absent from the prostomium, the ventral bundles of XI and 

 2 or 3 caudal somites. Preclitellar bundles contain 4 to 6, usually 5 

 setae; behind the clitellum are found at first 4, then 3, and toward the 

 posterior end 2. Smaller numbers are very likely to occur in the doi-sal 

 bundles, though there is no constancy in this respect. There are no 



