PARTULA FILOSA. 83 
the main valley cutting (plate 18a). At 550 feet altitude, about 3.5 miles from the 
shore, the valley trends suddenly to the east, then to the west, and the stream-bed 
rises more rapidly. As a result this part is more open, although its sides are 
covered by dense vegetation, owing to the great amount of rain that falls upon 
these interior heights (plate 18h). Nevertheless, the snails are few in number and 
exist only a short distance beyond. 
The food-habits of fi/osa, and indeed all of its ecological relations, are in no wise 
peculiar. The snails are less sensitive to day-time changes in moisture than are 
hyalina and clara, for only the younger immature individuals become active after a 
shower of rain, so far as observations have been made. 
THE SHELL OF PARTULA FILOSA AND ITS VARIATION. 
Though this species inhabits only a single valley, the range of its color-variation 
is greater than in the case of the widespread unbanded varieties of clara. In addi- 
tion, the shells of the upper and lower portions of the valley differ as much in 
structural respects as do many of the neighboring but separated valley colonies of 
clara and hyalina. In brief, this species is far from being invariable, even though 
it is so sharply restricted geographically. 
Tas e 32.—Partula filosa. Puirai Valley. 
MEAN VALUE. 
Shell. Aperture. Length aper- 
: ture + length 
Series. No. shell, pro- 
Length. Width. Proportions. Length. Width. Proportions. portions. 
mm. mm. p. ct. mm. mm. Dd. ct. Dp. ct. 
Whole valley (all years)| 209 | 14.1572 .0295| 9.1029+.0161 64.2751+ .1029 | 7.6292+.0182| 6.4541+.0151 | 84.4761 .1489 | 53.7536+ .0838 
Upper valley (1909)...} 122 | 13.9754+.0337| 9.0262 .0193 64.5410 .1279| 7.5311+.0200| 6.3738+.0192 | 84.5902 += .1902 | 53.7213 +.1083 
Lower valley (1906)...| 52 | 14.4904 .0581| 9.2654 .0339 | 63.9115+.2046| 7.8423+.0404| 6.6615 .0279 | 84.8269 = .3284 | 53.9615 + .1838 
Difference, 1906:1909.. 
+.5150+.0671 
+.2392 + .0390 
[—.6295+ .2413]) +.3112+.0451 
+.2877 + .0339 
[-+.2367 + .3795]|[ +.2402 + .2133] 
i 
STANDARD DEVIATION. 
Whole valley (all years)| 209 | 0.6338+.0209| 0.3452+.0114| 2.2074+.0728)| 0.3913+.0129| 0.3241+.0107| 3.1945+.1054) 1.7978+.0593 
Upper valley (1909)...| 122 -5524+ .0239 -3159+ 0136] 2.0936+.0904 .3279 + .0142 -3138= .0136} 3.1126+.1345] 1.7718+.0765 
Lower valley (1906)...| 52 -6213+ .0411 .3631+.0240| 2.1879+.1446 4320+ .0286 -2988+ .0196| 3.5121+.2321| 1.9656+.1299 
{ —.0150+ .0239]][ +-.3995 + .2682]|[ +.1938 + .1889] 
Difference, 1906:1909.. . |[-+.0689 = .0475]|[ +-.0472 + .0276][ +.0943 + .1705]| +.1041 = .0319 
Considering first the structural characters of the shells and their variation, 
we may add to the qualitative descriptions of earlier authors the precise statistical 
determinations of the whole measurable series of adult shells (table 32). In the 
next place, we may compare the shells taken from the upper part of the range 
in 1909 with those obtained in 1906 from the lower areas, with the result that marked 
differences are brought to light which are demonstrated both by the statistics 
(table 32) and the graphic representations of table 33. Specifically, the lower asso- 
ciation consists of shells that are longer and wider, but narrower, with probability 
even if not with statistical certainty. The apertures are also longer and wider 
