280 THE CHICAGO ACADEMY OF SCIENCES. 



and has presented the set showing age-development to the 

 Academy. Considerable variation is shown in the form ot the 

 shell, the young (twelve to sixteen weeks) looking very likeZ. 

 palustris, the characteristic "twist" of reflexa not appearing until 

 the twenty-first week. The measurements of the successive 

 stages are as follows: 



Weeks; length, 2.00; width, 1.50 mill. 



^OO; 2.75 " ) This set shows that some indi- 



10.00; " 5.00 " ) viduals grow iaster than others. 



13.00; " 6.00 " 



20.50; " 7.50 " 



21.50; " 9.00 " 



25.00; " 9.00 " 



26.50; " 9.50 " 



26.00; " 11.50 " 



28.50; " 10.50 " 



Another remarkable set showing development was pre- 

 sented by Dr. Lyon. The tablet contains fifteen specimens 

 which were all killed when seventeen weeks old, yet the small- 

 est is 4 mill, long and the largest 27 mill. All were fed on 

 lettuce and contained in a 4-quart battery jar, under equal con- 

 ditions of heat and light, and the brood was from a single egg 

 capsule. 



ii2a. Limiwea reflexa jolietensis Baker, pi. xxxii, fig. 4. 



Limncea attenuata BAKER (non SAY), Trans. St. Louis Acad. Sci., Vol. 



IX, p. 20, pl.i, fig. 4, 1901. 

 Limncea reflexa jolietensis BAKER, The Nautilus, Vol. XV, p. 17, 1901. 



Shell: With an attenuated spire, which is more pointed 

 than in reflexa; whorls seven, somewhat loosely coiled, very 

 convex; leaving a well-marked suture; apex small, rounded, 

 prominent; aperture about a third the length of the entire 

 shell, lunate, thickened on the inside by a heavy callus; peri- 

 stome thin; columella covered by a heavy callus and with a 

 prominent plait; color light horn, sometimes darker, aperture 

 dark horn, the callus yellowish, bordered with dark brown; 

 other characters as in reflexa. 



Length, 24.00; width, 8.00; aperture length, 9.50; width, 5.25 mill. (12309.) 



23.00; " 7.75; " " 9.00; " 5.00 " (12309.) 



22.00; " 7.00; " " 8.75; " 4.75 " (12309.) 



29.00; mill. (Walker collection). 



Animal, jaw and dentition as in reflexa. 

 Genitalia: Not examined. 



