FRESH WATER MUSSEL SHELLS 135 
trast, that up to 12 years the increase is more like an inch for this 
species. 
In a related form, Quadrula (Fusconaja) undata, the last inves- 
tigators cited give 15.8 mm. as the length of a pond raised specimen 
at the close of the second year. This checks fairly well with my 
estimate of 2 year specimens of F. flava, as well as does the increase 
in two years of .44 in. which equals 11.17 mm. 
2. AMBLEMA PLICATA 
No. 
Spec. Age E DVD) Fs)SP PD AD PHL. ~ AHL’ . ‘TE, 
-13cm. 1.74cem. 1.05cm. 1.65cm. .50cm. 1.2lcm. .50cm. .144cm. 
17% 115% 147% PSS = hie 11% «110% 111% 
63% 152% 145% 163% 154% 150% 120% 200% 
95% 186% 108% 200% 172% 182% 176% 166% 
47% 250% 265% 271% 163% 200% 145% 225% 
288% 280% 260% 300% 240% 290% 220% 270% 
289% 260% 270% 301 % 220% 262% 246% 298% 
312% 284% 276% 300% 246% 300% 250% 222% 
10 339% 319% 279% 398% 220% 348% 260% 244% 
Il 265% 244% 288% 280% 222% 244% 184% 285% 
12 338% 328% 295% 360% 260% 350% 290% 235% 
13 3509, 5 332% 310% 381% 354% 362% 310% 290% 
14 409% 364% 316% 440% 292% 390% 410% 444% 
15 410% 362% 380% 454% 260% 4215% 356% 357% 
16 403% 352% 368% 436% 286% 429% 332% 421 %Z 
verage growth per year in each dimension for 16 years, 
166% 147% 142% 182% 104% 170% 125% 12% 
OMOMNAN BW 
BD WWWW WWW WW WWW WWW 
Depuctions From TABLE oF PERCENTAGES AND REMARKS. 
‘ 
In this species, the dimensions of L, PD, and PHL increase most 
greatly with age. DVD and DSD increase at about the same rate. 
T'H and AD show the least increase. Increase in size is continuous 
from year to year, but shells 14-15 years of age are as large as some 
older ones. From the ages 8-12, DVD and DSD increase more 
rapidly than in early years, as do also PD and PHL. While _ the 
increase in 7'H is relatively less, that in AHL is relatively more. 
This species is most likely the one studied by Isely, (Quadrula 
undulata). In young specimens, (p. 10), he observed a gain of 21% 
in length, 20% in height, and 19% in breadth. In my specimens, 
the ones most corresponding with his in dimensions are aged 6, 8 and 
9 years. My specimens for those years check up length 20%, 
height 22%, breadth, 1%. The small number of variants used might 
explain the greater discrepancy between these, or the fact that lake 
dwelling forms are usually smaller than river specimens, even earlier 
