PARTULA GIBBA, SAIPAN. 103 
the body-whorl develops, it is impossible to separate the adolescents from those 
of mitella. 
The final class, castanea, comprises within its two orders the darkest and most 
richly colored shells of the species (fig. 38 to 57, plate 14). As inthe major group of 
Guam with the same name, the general color is brown, and the apex if not the 
whole spire is deeply colored with brown, red-brown, or purple-brown; it is this 
feature which distinguishes the shells from those of the so-called phzea class of 
Guam. The two orders are separated on the basis of their respective ruddy or 
purplish admixtures to the fundamental brown; such colors are continued upon the 
flaring lip, often with intensified brilliance. Because the last characteristic is 
peculiar to the castanea of Saipan, the names rubescens and purpurescens are em- 
ployed instead of rubra and purpurea, which applied to the corresponding orders 
in Guam. 
The typical shells of castanea-rubescens, with dark red-brown inner and outer 
surfaces and with full-tinted lip, are shown in figures 41 to 48, plate 14 At Puntan 
Flores, and more sparingly at a few other places, an interesting variant was found 
with lightened but still ruddy colors and with the uppermost whorls diluted in color 
along the suture toward the apex (figs. 38 to 40, plate 14); the inner wall and the lip 
are also lighter. During their growth, the rubescens shells are at first corneous- 
brown, with deeply colored apex (figs. 47 to 49, plate 14); later the tones gradually 
darken, the apical color extends and deepens, and finally the distinctive ruddy color 
appears as maturity approaches. 
The purpurescens order is much less abundant, and unmistakable examples 
were found only in two localities (figs. 50 to 57, plate 14). The shells are invariably 
dark purplish brown within as well as without, and the lip is typically faint purple 
in color. The Fanaganam examples displayed a yellowish instead of a purplish 
tinge upon the lip (figs. 52, 53, plate 14). Decortication occurs in occasional 
instances (figs. 55 to 57, plate 14). 
The distribution of the foregoing classes is far from uniform as the census 
table shows (table 50), and the differences displayed by the several local series are 
entirely independent of the environmental circumstances so far as observation goes. 
The smaller collection from the isolated summit of Torre comprises only bicolor 
and castanea-rubescens, while the Fanaganam series includes all 6 of the kinds found 
in Saipan. The relative numbers of the constituent color-groups vary so that 
even when the same classes are present in two different areas such as Chalankiya 
and Puntan Muchut the colonial complexions in color respects are markedly unlike. 
The point has already been noted that it is not the color-class mitella which 
is universally present, but bicolor; and the same is true of castanea so far as the 8 
areas of investigation are concerned; the castenea of Guam were few and scattered. 
At the extreme northern and southern areas in Saipan, mitella is more abundant 
than in the intermediate territory, while in the fuller series of stations of Guam it 
was bicolor that was so distributed. The color-order castanea-purpurescens OCCUrS 
in the higher locality of Fanaganam and on the flat land south of Garapan with 
open cultivated areas intervening; it may be a sporadic product from castanea- 
