A. M Verrill — Mar me Planaricms of New England. 493 



genital opening. Female genital organ with a glandular accessory 

 vesicle. 



The following species is referred to this genus chiefly on account 

 of its external resemblance to the tyi>ical species. 1 have had no 

 mature specimens sufficiently well preserved to enable me to study 

 the reproductive organs. 



Discocells mutabilis Vemii. 



Polycelis mutabilis Verrill, Report ou the Invertel). of Viueyard Sound, etc., p. 



746, (452,) 1873. 

 Lang, op. cit., p. 616, copy of original description. 



Plate xl, figure 7; Plate xlh, figures 6, 6a, 7. 



Description of the original specimen from life: — Body much 

 depressed, thin, changeable in form, often elliptical or oval, fre- 

 quently broad and emarginate in front, and tapered posteriorly. 

 Marginal ocelli very distinct, black, forming several rows along the 

 front border, l)ut only one or two rows laterally. Dorsal and cere- 

 bral ocelli larger, forming three pairs of rather ill-defined clusters ; 

 the outer or dorsal clusters are largest, often convergent backward ; 

 a pair of smaller cerebral clusters is situated a little in advance, and 

 nearer together ; the third pair is a little farther forward and still 

 closer together, often more or less confused with those next behind 

 them. 



Color, yellowish brown, darker centrally ; or pale yellowish, thickly 

 specked with yellowish brown. Length, about V to 9™'" ; breadth, 

 5 to 6°>"'. 



Thimble Islands, near New Haven, Conn., 1 to 2 fathoms, among 

 red algfe, 1872. 



The original type-specimen, described above, was mounted in bal- 

 sam for the microscope, when first obtained. It is still in my pos- 

 session, and from it the figures (PI. xlii, figs. 6, 6a) have been 

 drawn with the camera-lucida. Unfortunately the internal organs 

 are not well preserved. The reproductive organs cannot be seen 

 at all. Possibly the specimen was immature, with imperfectly de- 

 veloped sexual organs, but its size would indicate that it was adult. 



The pharynx and stomach are large and have numerous lateral 

 obes. As near as can be made out, the elongated stomach has eight 

 or nine principal branches on each side, but they are indistinct, owing 

 to the poor state of preservation of the specimen. 



The marginal ocelli are rather conspicuous and extend back nearly 

 as far as the posterior end of the stomach. The four groups of 



