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 like Z. 
palustris, the characteristic “twist” of refexa not appearing until 
the twenty-first week. The measurements of the successive 
stages are as follows: 
6 Weeks; length, 2.00; width, 1.50 mill. 
12 iy * 5.00; pee A) Ti This set shows that some indi- 
12 “ “10.00; “ 500 « viduals grow faster than others. 
16 * 4, 1800)": - Sn60e—* 
16 MOO; 72 Bae 
4 ee ae «“ 2150; -* 9100 “ 
a2) 4 * 2600; #9002 4 
33 3 “26.50; o, BO 
52 e «26.00; “, ASD 
52 < « 28.50; 4 1050>7 
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 ina 4-quart battery jar, under equal con- 
ditions of heat and light, and the brood was from a single egg 
capsule. 
112a. Limnza reflexa jolietensis Baker, p]. xxxii, fig. 4. 
Limnea attenuata BAKER (non SAy), Trans. St. Louis Acad. Sci., Vol. 
IX, p. 20, pl.i, fig. 4, 1901. 
Limnea 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 bya 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 refiexa. 
i ai 24.00; width, 8.00; aperture length, 9.50; width, 5.25 mill. (12309.) 
23.00; mig {5 * - 9.00; « 5.00 “ (12309.) 
se 22.00 5 SOO; ce 4 8.75; “« 4.75 “ (12309.) 
“< 29.00; mill. (Walker collection). 
Animal, jaw and dentition as in reflexa. 
Genttalia: Not examined. 
er ee ee NS ee a eee ee eS ee oy 
