PARTULA OTAHEITANA. 159 
Either some of the yellow young are destined to become red in later life (for 
which there is some evidence, to be adduced below) or else the process of elimina- 
tion bears most heavily upon the lighter-colored individuals during post-embryonic 
life, to an extent which brings the 60 per cent of yellow young down to about 30 
per cent by the time maturity is attained by the survivors. Possibly the color- 
complexion of the whole population is changing from a preponderating red to a 
preponderating yellow. ‘This supposition is one which can be directly tested only 
by an examination of the Papenoo Partulz after the lapse of a few years. 
FAARUMAI, TIAREI, AND MAHAENA VALLEYS. } 
In the collections from five valleys of the sector immediately to the eastward of 
Papenoo, rubescens is exceedingly rare or absent. It does not appear among 600 
adults from Farapa, a valley that lies next to Papenoo, and is also missing in a series 
of more than 400 mature snails from Vahu, the fifth valley to the east of Papenoo. 
The significance of the rarity or absence of this form, in places that support large 
and flourishing colonies of P. 0. affinis, needs no further discussion. 
TaBLe 99.—Partula otaheitana rubescens, Faarumai, Tiarei, and Mahaena Valleys. General statistical description. 
MEAN VALUE. 
Shell. 3 Aperture. Length aper- 
[Rae ae a cies es ee ee |e we a) ee il) sture length 
Valley. NO: shell, propor- 
Length. Width. Proportions. Length. Width. Proportions. tions. 
mm. mm. p. ct. mm. mm. p. ct. p. ct. 
Faarumai....| 19 | 20.5395+.1382] 11.8578+.0907| 57.6569+.5225| 10.7632 .0689] 8.2053==.0628| 76.4474 .3839| 52.2368+.3129 
phiarelaceri- 15 | 19.9833+.1266] 11.6467+.0746] 58.3000+.5135] 10.2733+.0538] 7.9000 .0492| 76.9000 + .5313} 51.3000+.2310 
Mahaena....} 6 | 18.5833+.1298] 11.1667+.0757| 60.0000+.5450] 9.8667=+.0668] 7.5667=.0519] 76.1667+.5877| 53.0000+.1377 
STANDARD DEVIATION. 
Faarumai....| 19 0.8931+.0977| 0.5861+.0641} 3.3758+.3695| 0.4450 0487| 0.4059+.0444| 2.4809+.2715] 2.0220+.2213 
INE oo 3a06 15 .7272 + .0895 -4287+.0527| 2.9484 .3631 -3087 + .0380} .2828+.0348} 3.0506+.3754| 1.3266+.1633 
Mahaena....| 6 .4713+.0918 2749+ 0535] 1.9791 .3854 -2427 + .0472| .1885+.0367| 2.1344+.4156 -5000 + .0974 
In the three valleys inhabited, the small collections present very different color 
complexes. In Faarumai, 7 out of 19 are yellow (plate 27, fig. 12) while the rest 
usually display a ruddy yellow-brown (plate 27, figs. 13 to 15) not exactly like the 
“red” of Papenoo shells. In Tiarei, 11 out of 15 are a beautiful yellow (plate 27, figs. 
16 and 17) sometimes with a deep purple apex; the others are “‘red”’ (plate 27, fig. 18). 
In Mahaena, finally, all of the 6 shells (plate 27, fig. 19) are clearly allies of the ‘“‘red”’ 
Papenoo examples. 
The statistical comparison of the three small series (table 99) is interesting 
because there is a regular and consistent reduction in all of the absolute measures 
in passing eastward. ‘The stoutness of the whole shell increases with similar con- 
sistency, but in the other proportionate measures there is no such regularity. 
In Faarumai no shell bears a pillar tooth. One of the 15 specimens from Tiarei 
shows a trace of this structure. Of the 6 shells from Mahaena, all possess well- 
developed prominences. 
