Baker — A Revision of the Limnaeas of Northern Illinois. 5 

 2. Limnaea catascopium Say. 



PI. I. f.9. 



Limnaea catascopium Say, Nich. Encycl. ed. 1. pi. 11. f. 3. 1816. 

 Limnaea virginiana Lamarck, An. sans Vert. ed. 1. 6: 160. 1822. 

 Limnaea cornea Vallenciennes, Recueil d'Observ. Zool. etc. 2:251. 1833, 

 Limnaea sericata Ziegler, Rossmassler Iconog. 1 : 98. 1837. 



/Shell: Thin, globosely ovate, inflated; color light horn to 

 blackish; surface dull to shining, lines of growth numerous, 

 fine, crowded, wavy; apex frequently eroded; whorls 5, 

 rounded, inflated, the last very large and inflated; spire sharp 

 to obtuse, conic ; sutures slightly impressed ; aperture roundly 

 ovate, large, from half to three fourths the length of the 

 entire shell, rounded below, somewhat narrowed above; peri- 

 stome thin, sharp, thickened by a light callus just within the 

 edge, the callus whitish ; columella oblique, with a heavy 

 plait across the middle ; the lower part of the columella has 

 a flexure caused by the heavy plait; the lower part of the 

 peristome and the whole of the columella are covered by a 

 heavy coating of white, testaceous material, which is reflected 

 over the umbilicus, completely closing it. 



Length 13.50; breadth 8.75; aperture length 8.00; breadth 5.00 mill. (8388.) 

 '« 14 50; " 9.50; " " 9.50; " 5.50 " (8388.) 



" 14.00; " 9.00; " " 8.75; " 5.00 " (8388.) 



Animal, jaw and radula not examined. 



Distribution: New England to Utah, British America to 

 Virginia. 



Geological Distribution: Pleistocene. 



Habitat: In the larger lakes and rivers, attached to sticks, 

 stones and various debris. 



Remarks: Catascopium is readily distinguished by its 

 large, rounded aperture and swollen whorls. The height of 

 the spire varies, in some specimens being one-half the length 

 of the aperture while in others they are about equal in 

 height. The long spiral form has not been collected in the 

 area under consideration, and is much more common in New 

 York State than in the west. 



2a. Limnaea catascopium pinguis Say. 

 Pi. I. f. 12. 

 Limnaea pinguis, Say, Journ. Phil. Acad. 5: 123. 1825. 



Shell: Differing from typical catascopium in being more 



