FRESH WATER MUSSEL SHELLS 145 
Coker, Shira, Howard and Clark, (2), report that this species 
attained a length of 41-47 mm. in two growing seasons, 65 mm. by 
August of the third growing season. Specimens 45-47 mm. in length, 
evidently in the second year of free life, were measured and planted 
in the Mississippi river by Lefevre and Curtis. When recovered by 
the former authors, they had attained a length of 81-85 mm. None 
of my specimens were so large at 4 years, the nearest corresponding 
being at 7-8 years, while the nearest specimen attaining a length 
of 81-85 mm. were between 12-13 years of age. Here again the 
environment may exercise a deterrent effect upon growth. The 
average increase in length of the specimens described by these 
authors—90 %—is far lower than the one I have derived. 
Tas_Le or AvEeRAGES INDICATING COMPARATIVE GROWTH OF 
Species STuDIED. 
de! oe 
@ |e be 
n ee ire aS 
=| ine] 
| 28] ot - 
Sol a/ 5.8 oe F 
Reta BS aos Average Yearly Increase in Dimensions 
3 § Plone ey aoe 
5 3) ° @ | = 5 he — 
2 %1z5'65%! L DVDDSD PD AD PHL AHL TH 
Fusconaja flava parvula..... 34| 12 |5 mm|143%/150% 209% | 161 %| 110%) 192% 11676, 87% 
Amblema plicata costata....| 45 | 16 |8.3mm/166% 147% 142% 182% |104%|170% 125% \12% 
Pleur. coccin. pauperculum..| 10| 12 |2.7mm| 4.6%|2.5% | 4%/6144% 714% 64% 614%/914% 
Elliptio dilatatus sterkii..... 28) 12 |7.1mm/|144% |160%|219%| 156%) 108% 172% 179% \285% 
Lasmigona costata eriganensis| 10| 10 |3.1mm) 4%) 5% 3.8%/|4.4%|1.6%| 4% 9.2%|7.6% 
Anodonta grandis footiana...| 14 9 |8.7mm| 34%| 29%) 32% 39%| 27% 3%) 28%| 16% 
Leptodea fragilis........... 22| 12 |10mm.| 61%) 57%| 59%| 73%| 67%| 68%) 42%| 42% 
Propteraraiatacip, sac sce 19 | 22 |\7.9mm|\260% 294% 364% |282% 280% |324% 129% 190% 
Anodontoides feruss. subcyl..| 17 9 |8.2mm| 26%) 8%) 33%) 26%) 33%| 27%, 32%| 39%. 
Dignmia rectasj5.5)0-<0 se hos 15| 18 |6.3mm| 57%| 72%) 81%) 59%) 74%| 79%) 72%|106% 
Lampsilis siliquoidea rosacea | 35-| 19 5.7mm| 26%) 25% 42%) 32%) 21%| 41%| 40%| 50% 
Lampsilis ouata conadensis..| 40 | 19 5.4mm 186% 206% 249%|210%| 47%|256%| 187% 106% 
The following is evident from the preceding table as to the 
average growth per year in the different groups of mussels, with 
regard to the dimension of length: . 
Hard shell, slow growing Quadrula mussels, 
(Species 2. Are cle cae Re takes 6:8 mm. or .27 in. 
Paper or thin shell, rapid growing mussels, 
KSpecics Gy PAD) on. cis Me ons ste aoo nwa. - Sums eRie aor ie. 
Intermediate or Lampsiline group mussels, « 
(apectesrSyclOrcddl p12). bine os See sc 82) MM On aS im 
The numbers of shells in the series representing Pleurobema and 
Lasmigona, were too small to be taken into consideration in this 
comparison. Comparing with the data cited from Coker, Shira, 
