228 INVERTEBRATA OF MASSACHUSETTS. 



Shell ovate-elongate, thick and strong, color varying from yel- 

 lowish-green to dark olive-green ; whorls five, regularly convex, 

 , inclining rather abruptly towards the suture, so as to form a mod- 

 erate shoulder ; surface marked with fine wrinkles of growth, and 

 occasional stripes of dark purplish, indicating the position of pre- 

 ceding apertures ; also with minute, revolving lines, which in 

 young specimens, when viewed in the water, are seen to be gar- 

 nished with fine, pubescent hairs ; two or three of the whorls at 

 the apex are usually broken off, leaving an irregular, eroded sur- 

 face ; aperture oval, not exceeding half the length of the entire 

 shell, forming an angle above ; lip simple, very sharp, until, as it 

 rises towards the columella, it becomes thickened, and, turning 

 outwards, forms a smooth, rounded margin, leaving no umbili- 

 cus ; a thick enamel spreads across the preceding whorl, margined 

 with purplish ; interior bluish. Operculum thin, ovate, beaked, 

 with a groove from the centre to the tip of the beak. Length 

 l-p\ inch, breadth /^ indi, divergence 56°. 



Animal with a broad, tongue-shaped foot, drawn out into an- 

 gles each side in front, of a livid olive-color varied with dark, 

 vivid-orange, transverse spots above, and minutely dotted with the 

 same beneath ; tentacula olive above, spotted with orange, lighter 

 below. Eyes on a niche at the exterior base of the tentacula. 



Found in ponds and muddy streams, usually concealed under 

 shelving banks, or imbedded an inch or two among loose mud and 

 roots. 



This is the only large species inhabiting the waters of New Eng- 

 land. It is less massive than P. ponderdsa, its whorls more convex, 

 and its aperture less elongated. It is less globular when young than 

 P. sub-purpiirea, and the spire in the adult more symmetrical. The 

 young are excluded in a living state with a shell of three complete 

 whorls. It is peculiar for the almost constant loss of its tip. 



Genus AMNICOLA, Gould and Hald. 



Shell ovate-conic, thin ; spire acute, composed of a few rounded 

 whorls ; aperture small, oblique, rounded-ovate ; lips continuous, 

 simple ; operculum horny, spiral, with a few volutions. 



