36 LIMNEA SOLIDA. 



aperture, but in most cases longer, and rarely 

 shorter. There is, however, little doubt about 

 these being the caperata, as they agree with 

 most of the characters given, and especially 

 with the description of the revolving lines. 

 These are so superficial, as to be readily re- 

 moved with a brush. 



Explanation of Plate 11. 



Figures 1, 2, 4, 6, 7, 8, are from specimens collected 

 from a spring of shallow running water, subject to being 

 dried up, and flowing into the Susquehanna at Marietta, 

 Pennsylvania. The bottom is a deep bed of black tena- 

 cious mud, covered with grass. 



Mr. Adams' specimens are from a somewhat similar 

 locality. Figure 3 is from an Illinois specimen; 5 from a 

 Vermont shell; whilst 9 represents 'L. umbilicata.' 



LIMNEA SOLIDA, Lea. 



Plate 11.— Figs. 10—13. 



L. testa conica, lsevi, subsolida, umbilicata; apice acuto: 

 anfractibus 4 — 5 convexis, sutura excavata: apertura sub- 

 ovata, decolorata. 



