IIo VARIATION, DISTRIBUTION, AND EVOLUTION OF THE GENUS PARTULA. 
respect is so great as to make the proportionate measure the lowest average in the 
whole series of colonies: “The comparison of Papehue, Aoua, and Orofere specimens 
brings out essentially the same relations that appear when the shells as wholes are 
compared. 
Finally, we may deal briefly with the proportion of aperture length to shell 
length. The “curve” of averages changes from valley to valley, like those of the 
foregoing characters. Its most interesting movement focuses about Maruapoo, 
where the shell length remains about what it was in Punaruu, while the aperture 
dimension decreases greatly; the result is a marked drop in the relative figure to 
the lowest average of the whole series of valley colonies. 
In brief, the statistical constants of the seven characters vary from colony to 
colony, to some extent in correlation, but not always in close correspondence. A 
relative reduction in shell length is not necessarily accompanied by a drop in aper- 
ture length or by an increase in shell proportions. Each valley bears a population 
with characteristic features. 
Now we may take into account the characteristics of color displayed by the 
shells of the seven colonies, which were ignored in the above statistical summary. 
It then appears that there are not seven independent and coequal types, each 
restricted to a single valley, but that only four primary divisions exist, as the detailed 
description has shown. The shells of Taapuna and Punaruu form together the 
primary variety composita, so called because its members fall into four well-marked 
color-classes to which individual names of a secondary order have been given, 
€. &.5 pallidior, trilineata, concrescens, and nodosa; an additional feature of this variety is 
the dextral coil, which is predominant (Taapuna) or virtually exclusive (Punaruu). 
In Maruapoo most of the shells differ from var. composita and the succeeding 
geographically circumscribed groups in statistical peculiarities, in coloration, and 
in the prevalent sinistral coil; for these reasons they require a distinctive varietal 
name, /e@va, chosen on account of the last-named character. As a group, although 
a small one, the shells of Atehi are minute, very stout, dextral, and plain brown; 
their small size is specified by the varietal name, exigua. Finally, the three valleys 
of Papehue, Aoua, and Orofere are inhabited by snails of this species that resemble 
composita in color-constitution, but their statistical characters and their geographical 
discontinuity set them apart from composita, as well as from leva and exigua for 
indicated reasons. Because a few of the shells in Papehue and Aoua approach the 
condition of exigua, this last section of P. nodosa has been called var. intermedia. 
At this point we must deal with a question which has been held in abeyance 
heretofore, namely, whether the differentiation into color-classes, as in the colonies 
of Taapuna and Aoua, is more or ess fundamental than the division into geographi- 
cally circumscribed groups which have been designated as primary varieties. Are 
pallidior, trilineata, etc., the real varieties and elementary species, represented by 
varying proportionate numbers in different valleys where, also, the details of ground- 
colors and patterns have changed, or are composita, leva, exigua, and intermedia 
the primary divisions of the species in the sense that they are more differentiated 
inter se than are their constituent color-classes? One consideration alone would 
lead us to regard the second classification as primary, and the former as subordinate. 
