PARTULA OTAHEITANA. 155 
The relative numbers of yellow and red snails are different for the three suc- 
| cessive areas of collection (table 93). While the figures for 1906 and 1908—outer 
| and intermediate areas—are not very diverse and refer to few individuals, yet their 
| comparison with the numbers for 19g09—inner area—shows that the red group 
undoubtedly diminishes in relative abundance in passing inland. 
TaBLeE 93.—Partula otaheitana rubescens, Papenoo Valley. 
Class frequencies. 
No. of 
adults. 
No. of 
yellow. 
No. of 
red. 
Per cent 
of red. 
Per cent 
of yellow. 
Area. 
72.85 
76.66 
64.28 
Lower valley 
Middle valley 
Upper valley........ 
Whole area 69.29 
Comparing the three annual series as wholes—. ¢., the yellow and red shells 
taken together—the coastward shells of 1906 differ distinctly from the intermediate 
series in absolute measures, and significantly so; in proportionate measures they are 
the same, allowing for the scope of the probable errors involved (table 94). The 
| inner series of 1909 differs from the intermediate group, it is true, but only in shell 
proportions, and perhaps in the pillar tooth, does the divergence approach a signifi- 
cant figure. Like P. otahettana amabilis and P. filosa of Pirai Valley, P. 0. rubescens 
of this region exhibits a reduction in size when snails of the interior are contrasted 
with those of the extreme outer edge of the inhabited area. Again it would seem 
that the logical reason for the facts is to be found in a more rigid elimination where 
conditions are less favorable, as in the lower dry part of the valley, where only the 
larger and more vigorous individuals can subsist. 
TaBLe 94.—Partula otaheitana rubescens, Papenoo Valley. Comparison of annual series. 
| Mean VALUE. 
Shell. Aperture. Length aper- 
ture + length ; 
shell) propor Tooth, index. 
Length. Width. Proportions. Length. Width. Proportions. tions. 
mm. mm. p. ct. mm. mm. Dp. ct. p. ct. 
| 1906 20.5785=+.0726| 11.3915+.0495) 55.1572+.2071| 10.4771+.0432 7.8315 .0407 | 74.6572 .2444| 50.7571+.1722| 2.8286+.0770 
| 1908 20.3430+ .0694| 11.2186+.0425}| 55.1163+.1464| 10.2675 .0385 7.6465 .0335 | 74.3721+.1917| 50.5349 .1351 2.2889 + .0744 
1909 20.3139+ .0453| 11.3078+.0263| 55.5723+.1203| 10.2989+ .0259 7.6734+.0215| 74.5500+.1582|] 50.6889 .0952 2.4651 + .0495 
All 20.3765 + .0340| 11.3024+.0207 | 55.3690+.0865| 10.3280+.0195| 7.6994+.0168| 74.5268+=.1104| 50.6637+.0714| 2.4828+.0371 
Dif. 
1906-1908 —.2355+.1004| —.1729+.0652 | [—.0409=.2536]) —.2096+.0578} —.1850=.0527 | [—.2850+.3106]| [—.2222+.2189]| —.5397+.1070 
if. 
| 1908-1909 [—.0291 + .0828]| [+.0892=+.0499]| +.4560+.1895 | [+.0314+ .0464]] [+.0269+ .0398]} [+.1779.2505]| [+.1540+.1652]] [+.1762 + .0893] 
STANDARD DEVIATION. 
1906 70) 0.9004.0513| 0.6138+.0350| 2.5684+.1464] 0.5362+.0305| 0.5052+.0288} 3.0314+.1728| 2.1360+.1218| 0.9557+.0544 
' 1908 86 -9539+ .0491 -5846 = .0300 2.0125+.1035 .5378 + .0272 .4610 + .0237 2.6360 + .1355 1.8580+ .0950 1.0461 + .0526 
1909 180) -9002 + .0320 .5242 + .0186 2.3922+ .0851 .5157 += .0183 -4281=+ .0152 3.1469+.1119 1.8936+ .0643 -9971 = .0350 
| All 336 -9246+ .0240 .5627+.0146| 2.3504+.0612 .5314 .0138 -4555+.0119| 3.0013+.0781 1.9395 + .0505 1.0172 .0262 
