THE NATURAL HISTORY SURVEY. 263 



105. Limiuea catascopium Say, pi. xxxi, fig. 5. 



LimncEa catascopium SAY, Nich. Encycl., ed. 1, pi. ii, fig. 3, 1816. 



Limncea cornea VALENCIENNES, Recueil d'Observ. Zool., etc., Vol. II, 

 p. 251, 1833. 



Limncea sericata ZIEGLER, Rossmassler Iconog., Vol. I, p. 98, 1737. 



LiiHH&a intertexta CURRIER, MSS., vide Bryant Walker, in letter. 

 Shell: Rather solid, ovate, inflated; color light horn to 

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

 fine, crowded, wavy, crossed by numerous impressed spiral 

 lines; apex small, rounded, chestnut colored; whorls five, 

 rounded, subinflated, the last large and somewhat inflated; spire 

 sharp to obtuse, conic; sutures impressed; aperture roundly 

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

 tire shell, rounded below; somewhat narrowed above; peris- 

 tome thin, sharp, thickened by a light, whitish callus just within 

 the edge; columella oblique, with a heavy plait across the mid- 

 dle; 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 is sometimes covered by a heavy coating of 

 white, testaceous material, which is reflected over the umbili- 

 cus, completely closing it. 



Length, 15.00; width, 7.50; aperture length, 8.00; width, 4.50 mill. 

 13.00; " 7.00; " " 7.50; " 4.00 " 



15.00; " 8.50; " " 9.00; " 4.50 " 



12.00; " 7.00; " " 7.00; " 4.00 " 



Animal, jaw, radula and genitalia not examined. 



Distribiition : New England to Utah, British America to 

 Virginia. 



Geological distribution : Pleistocene. 



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

 stones and debris. 



Remarks: Catascopium is readily distinguished by its large 

 aperture, and well rounded whorls. The height of the spire 

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

 aperture (var. pinguis} and in others they are about equal. 

 In the typical form the spire is gracefully conical, and the 

 aperture and lower part of the shell are evenly rounded. The 

 only species with which this species can be confounded is 

 Limnaa palustris, but that species is generally larger, the spire 

 is sharper and generally longer, and the surface is malleated, 

 while catascopium is not. A comparison of the figures of the 

 two species will suffice to separate them. Catascopium seems 



