CHAPTER V. 
PARTULA FILOSA Pfeiffer. 
GENERAL CONSIDERATIONS. 
Partula filosa is a small dextral species that exists solely in Pirai Valley, a large 
topographical element of the second grade of size, situated in the drier northwestern 
part of Tahiti nui. Its sharp restriction in habitat is a feature shared with only 
two or three others of the three score species of the genus living in the Society 
Islands, and places jilosa at the opposite extreme from hyalina, whose range extends 
not only throughout Tahiti but also to islands of two other groups as well. Not- 
withstanding its occurrence in only one valley, filosa displays a variability which 
in certain respects exceeds that of some species inhabiting several separated but 
neighboring valleys of a large island sector. ‘This species is clearly distinguishable 
from all others of its island; only Reeve has confused it with another form—an 
abbreviated variety of P. otaheitana. 
Pfeiffer’s original description (Proc. Zool. Soc., 1851), translated in Pilsbry, is as 
follows: 
“Shell perforate, conic-ovate, solid, sculptured with impressed spiral lines, hardly 
shining; chestnut-colored, ornamented with ashen hair-lines. Spire conic, rather obtuse. 
Whorls 5, flattened, the last as long as the spire, more convex, columella slightly plicate 
above. Aperture a little oblique, sub-triangular-semioval; peristome a little expanded, 
provided with a thick prominent callus within. Length 16, diam.8'% mm. long, 6% wide. 
Hab. Navigators Islands.” 
The locality given is erroneous, for neither ji/osa nor any similar species occurs 
in the group mentioned, which is now called the Samoan Islands. 
Pease’s description of this species as P. lineolata (Amer. Journ. Conch., 1867) 
adds nothing essential to that of Pfeiffer; his shells were dark examples like the 
earlier author’s types, but he speaks of “var. pale straw color or light reddish 
brown.” He gives the correct locality, Tahiti, and expresses the opinion that 
lineolata is “allied to P. filosa Pfr., inhabiting the Samoan Islands.” Asa matter of 
fact, filosa and lineolata are identical. 
Garrett (1884) comments as follows: 
“This small and well-characterized species is restricted to the lower portion of Pirai 
Valley, on the northwest coast of Tahiti, where it is abundant on foliage... . It is a 
solid, ovate-conic, chestnut-colored shell, marked by longitudinal cinereous strigations, and 
constant tuberculiform parietal tooth. The aperture is rather small, semi-oval, consider- 
ably contracted by the white, convex outer lip. It is never encircled by bands. Examples 
of a pale straw or flesh tint are not infrequent.” 
Mayer (1898) also found filosa in Pirai Valley, where it formed 17.6 per cent of 
his collection of 164 snails, a figure that is not far from my own number of 16.8 
per cent out of a total series of 1,254 adult individuals. Mayer adds certain impor- 
tant observations on the color relations of embryonic snails to those of their parents. 
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