PARTULA OTAHEITANA. 241 
Moaroa AND TAHARUA VALLEYS. 
Although these two valleys are entirely independent, their simzstrorsa associa- 
tions present so many features in common that they may be taken together. The 
snails of the second one constitute the last colony of sinistrorsa proper, for beyond 
them the shells belong to s7nistralts. 
The color-types represented are cestata and phea. In Moaroa the relative num- 
bers of the two classes were 39.4 and 60.6 per cent, respectively, in a series of 434 
adults; they were all sinistral. Three banded cestata were taken in Taharua; of 
the 322 sinistral snails, 35.7 per cent were cestata and 64.3 per cent were unbanded. 
The figures for the relative abundance of the two classes are thus substantially alike. 
Taking the Moaroa colony first, the phea division is quite heterogeneous, as 
in Faarahi, for the shells grade from rich dark-brown (solida) through confluens to 
strigated (striata), and finally clearer lighter-brown (plate 31, figs. 41 to 46). A very 
peculiar giant adolescent was secured here (plate 31, fig. 47) that greatly exceeds 
the largest adult in size. The medium and darker shells amount to 227, while the 
lighter variants number 36. Shells of the cestata are also variable, sometimes 
exhibiting much lightened and narrowed bands on a clearer background, sometimes 
becoming almost solid brown by the suffusion and extension of the revolving 
stripes (plate 31, figs. 48 to 51). An unusually small or “dwarfed” shell is shown 
in figure 51. Just as the phea class becomes resolved into more clearly demar- 
cated subdivisions in passing onward to the western sinzstralis series, so cestata 
breaks up into subordinate orders in more western valleys, as we shall see at a 
later point. , 
Passing to Taharua, we find phea centering about three grades of intensity. 
Out of 207 specimens, 19 are very light, clear, horny yellow (plate 31, figs. 52 and 53), 
I2I are medium, and 67 are dark confluens. It is possible that the first subdivision 
is really equivalent to apex without the dark coloring of the spire, but it is more 
probable that they are highly modified members of the phea color-class. The cestata 
class is composite, as in Moaroa; plate 31, figure 54 shows a very dark example. 
The lighter tone is exhibited by two of the dextral cestata (plate 31, fig. 55), while 
the third (plate 31, fig. 56) exhibits much suffusion of the stripes. 
As in their color-composition, so in their dimensions and proportions (table 
188) the two associations are very similar. In each case, also, the two constituent 
color-classes agree closely. ‘The aberrant dextral individuals of Taharua depart 
greatly from the average conditions of the prevalent sinistral series, so far as the 
absolute dimensions are concerned, but their proportionate measures are not dis- 
tinctive. Even in statistical respects they prove to be related to the rest, while 
positive but meager data of heredity establish their genetic relationship beyond 
a doubt. 
It so happens that both collections were made in 1906, during the wet season. 
As might be expected from the facts given heretofore, the rate of productivity was 
low (table 189), both as regards the numbers of gravid adults and also the numbers 
of embryonic individuals. 
