68 VARIATION, DISTRIBUTION, AND EVOLUTION OF THE GENUS PARTULA. 
Otuna Valley.—Of 13 shells, 11 were light and 2 were dark. The latter agree 
closely with the measurable examples of the former class, as far as structural charac- 
ters are concerned. ‘The figures given in table 25 refer to the entire group; 3 light 
individuals contained 6 similar young, while 1 dark specimen bore 2 dark young. 
Opiriroa Valley.—All of the 8 shells were banded (figs. 5, 6, and 7, plate 21) and 
5 of the animals bore 8 banded young; no unmarked young shells were present. 
This is a well-established color form that breeds true to its distinctive character, like 
nearly all of the banded specimens of clara which supply reliable data. 
In the details of the banded pattern, these shells are unique. A major stripe 
is sharply marked in most of them, and this corresponds with the single narrow 
band of the Tiamao shells described above. In addition, there are sutural and 
umbilical bands, less clearly marked, while midway between the major stripe and 
the sutural band there is another vague marking. A certain amount of suffusion 
between the bands occurs in allof the specimens. In structural characters (table 25) 
the shells differ somewhat from those of contiguous valleys. 
Temarua and Papeiti Valleys—These valleys are virtually divisions of one 
large element. From Orofere Valley, on the western side, to this point, the ravines 
are relatively narrow and shallow, but on passing Tearatapu, one finds in Temarua 
a valley of the largest class, both as regards its width and inward radial extent. 
The boundary ridge on the west is very steep and high (plate 17a). A long spur 
from the mass which is crowned by Mount Tetufera divides upper Temarua from 
Papeiti, the lesser branch. ‘This spur terminates about a mile from the shore and 
at some distance inland from the buttresses which form the limits of the valley’s 
mouth. Snails are not numerous, however, until the valleys separate. All of the 
individuals of clara were taken within the two valleys, and hence they may be 
viewed as two distinct series, even though of necessity these must be closely related 
to each other, as the figures demonstrate. 
The 5 adult examples from Temarua were all light; 4 were gravid and con- 
tained 5 light young snails. 
Of 9 adults from Papeiti, 5 were light, but none bore advanced young; 2 of the 
4 dark individuals contained 4 medium young, not quite as dark as their parents 
Teohu Valley.—This is a small gully in the triangular land-mass, between 
Temarua and Taharua, which rises inland to the peak of Mount Tetufera. The 
outward slopes of the terminal ridges are thickly covered with vegetation of low 
growth and, as much rain falls on this side of the island, these slopes are sufficiently 
moist to form a suitable habitat for clara, as well as for otaheitana and hyalina. 
Most of the specimens, however, were taken within Teohu Valley itself, where they 
are relatively abundant, forming 8 per cent of the whole snail population. 
In Teohu and its neighborhood, the shell is especially thin, and the black 
reticulated pigment of the mantle-wall is distinctly visible through the shell. 
The light individuals (fig. 8, plate 21) preponderate, numbering 27 out of 35; 
10 were gravid and provided 13 light-colored young; of the 8 dark-shelled animals 
(fig. 9, plate 21), 2 were gravid and contained 4 dark-shelled young. One of the 
