Partula cuneata, new species
Figure 3A
Shell dextral, elongate ovate-conic, moderately solid. Umbilicus openly
rimate. Whorls five. Suture impressed, not margined with a white line.
Spire conic, with somewhat pointed apex; smallest whorls convex,
penultimate whorl less rounded. Surface smooth and shining, with weak
1956 CRAMPTON: LAND SNAILS 9
and intermittent lines of growth. Spiral sculpture absent on the apex,
weak on the apical whorls, weak on the upper third of the penultimate
and last whorls, evanescent elsewhere.
Aperture unusually small, roundly elliptical, with vertical axis. Lip
well developed, calloused within, and uniform in width to the outer
terminus; hence the aperture is not subauriculate. The labial carina is
present as an uninterrupted ridge, within which the peristome is definitely
beveled. The columella is only slightly widened. The columellar
peristome is not thickened, and it bears a shallow notch close to the
inner insertion. Parietal callus exceedingly thin, with a very weak and
slightly arched border. Parietal tooth little more than a trace.
The general color of the shell is pale cream-corneous, devoid of transverse
strigations of dark color. The first two whorls are uniform purplebrown,
while the third whorl is bicolored owing to the disappearance of
the deep color below the suture and the continuation of the deep color
on the lower half of the whorl. The deeply colored spiral diminishes in
width as it continues onto the fourth whorl, until it vanishes at the beginning
of the last whorl. The lip is white and shining.
MEASUREMENTS OF HOLOTYPE: Shell length, 17.3 mm.; shell width,
10.2 mm.; shell proportions, 58.5 per cent; aperture length, 8.7 mm.;
aperture width, 6.8 mm.; aperture proportions, 78.2 per cent; aperture
length divided by shell length, 50.3 per cent.
HABITAT: Ereeo Valley, Raiatea, Society Islands. Arboreal.
The unique and distinctive nature of the sole example of P. cuneata is
emphasized by its contrasts with the five other species of Partula which
inhabit the same valley of Ereeo. The revolving bicolored pattern of the
middle whorls of the spire is not duplicated in any other shell of another
species dwelling in this valley or elsewhere in Raiatea, and by itself this
character is sufficient to justify the primary and independent status accorded
to P. cuneata. Structural features of equal significance are the
general form of the whole shell, the small size of the aperture, and the
brevity of the main axis of the aperture in relation to the length of the
entire shell. The exiguous parietal callus and the abrupt inward bend
of the outer terminus of the lip are also noteworthy.
The animal was gravid and contained two embryos together with one
egg of conventional nature. The embryonic shells were very light in tint,
and they exhibited no indication of the future dark color of an adult protoconch
or of a contrasting spiral helix.
Like the preceding species of very different character, P. cuneata is
regarded as a member of the '"garretti group" which from an earlier
common ancestor has proceeded along different lines from those of its
fellows in Ereeo Valley and in other areas of Raiatea.
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