FAMILY LIMNIADjE PLANORBIS. 61 



Planorbis MEGASTOMA. 



PLATE IV. FIGS. 60 <fc 61. 



(STATE COLLECTION.) 



Description. Shell large, coarse and solid. Whorls nearly five, rounded, with coarse trans- 

 verse waving wrinkles, becoming larger towards the mouth. A large prominence on the body- 

 whorl nearly opposite to the aperture, producing an obtuse angle. Spire depressed, with 

 the suture distinct ; beneath, the volutions are exhibited nearly to the apex. Mouth dilated, 

 but somewhat contracted at the margin, 0-3 wide and 0-4 high; its lower portion rounded, 

 arising from the lower part of the penultimate whorl ; line of the upper margin more nearly 

 straight. In the young (fig. 60), the aperture is not so much dilated, and is obscurely trigonal, 

 with the lower margin beneath the plane of the transverse diameter of the shell. 



Color. Olivaceous, tinged with yellowish within the aperture. In the young, black, with 

 the interior of the aperture dull reddish. 



Diameter, 0-8. Height, 0-3. 



This planorbis was found near Lake Ontario, and appears to be different from any species 

 yet described. In its aperture it resembles the small P. dilatatus of Gould, but is otherwise 

 very distinct. 



Planorbis campanulatus. 



PLATE V. FIG. 99* a. b. 



(STATE COLLECTION.) 



Planorbis campanulas. Say, Jour. Acad. Nat. Sc. Vol. 2, p. 266. 



P. id. Adams, American Journal of Science, Vol. 40, p. 269. 



P. id. Goold, Invertebrata of Massachusetts, p. 204, fig. 133. 



Description. Shell regular, small, transverse lines and grooves ; with four whorls above, 

 which are carinated, and form a conspicuous cavity ; beneath much deeper, and nearly per- 

 forating the shell to the apex. Aperture suddenly dilated, and subtrigonal or bell-shaped ; its 

 upper margin being elevated above the plane of the shell. 



Color. Light olive-green ; aperture brownish, polished. 



Greatest diameter, - 5. Height, - 2. 



This species occurs in most of the lakes in the western district of the State. 



