34 bulletin: museum of comparative zoology. 



2. Glossiphonia fusca sp. nov. 



Plate 4. 



a. Habitat, Form, Size, Color, 



This species is rather closely related structurally to G. stagnalis, with which 

 I have found it associated in the vicinity of Cambridge, Mass., and Trenton, 

 New Jersey. It is of about the same size as Gr. stagnalis, but is broader in 

 proportion to its length (Figure 13, Plate 4). In its movements it is some- 

 what more sluggish than that species and does not stretch itself to so great 

 a length. 



Length of largest individuals, fully extended, 20 inm.; at rest, 9 mm. 



Greatest width, when fully extended, 2.5 mm. ; at rest, 4 mm. 



Color, a coflfee-brown above, somewhat lighter below. The general brown 

 coloration is due to the presence in the superficial layers of the body of slender, 

 branched, thread-like pigment cells bearing numerous knot-like swellings and 

 tilled vdth. a dark-brown pigment. Such pigment cells are clearly homologous 

 with the pigment cells found in a superficial position in the body of G. stag- 

 nalis, — Graf's " excretophores." They are much more abundant on the dorsal 

 than on the ventral surface. On the former they appear in greatest numbers 

 in a median dark band about as wide as two or three body rings ; but they are 

 entirely wanting anterior to the eyes and in the following regions, which 

 therefore appear as clear, transparent areas ; — 



1. A transverse row of circular spots found on the sensory ring of each 

 somite. These spots are about the width of a ring in diameter. Their maxi- 

 mum number is seven, but it is a rare occurrence to find all seven present in 

 a single somite. Each, spot occupies a definite position on its ring, so that 

 those of successive somites form seven longitudinal rows, three in each half of 

 the body and one median in position. The paired rows may be designated as 

 marginal, intermediate, and paramedian, for they occupy positions which cor- 

 respond closely with those of the rows of dorsal papillae so designated in the 

 case of G. parasitica (Plate 2, Figure 6). 



The paramedian rows of clear spots are more constant in occurrence than any 

 of the others ; they can usually be found on somites v.-xxvi. The intermediate 

 and marginal rows usually begin about in the region of the genital pores and 

 continue with increasing distinctness back to the anus. The median row 

 is less well developed than any of the others. It is represented b}' an oc- 

 casional clear spot in the region posterior to the genital pores and anterior to 

 somite xxii. 



2. In the region of somites xxii.-xxvi., the median row of clear spots is 

 suddenly replaced by a continuous clear band about as wide as one of the spots. 

 Along the margins of this clear band, the pigment is unusually abundant, 

 which fact adds by contrast to the conspicuousness of the median band. 



3. The margin of the posterior sucker, where it projects beyond the outline 

 of the body as seen in dorsal view, usually bears eight or ten triangular or 



