Partula atilis, new species
Figure 3E, F
Shell dextral, stoutly ovate-conic, and solid. Umbilicus openly pyriform.
Whorls five. Spire short and stout, with slightly convex whorls;
the last whorl is somewhat tumose, and the apex is obtuse. Surface dull
and rough owing to the numerous and coarse lines of incremental growth.
The revolving incised lines are straight and well separated; they are
more or less obsolete on the last whorl. Suture vaguely impressed on the
body whorl and usually margined with a thread-like white line.
14 AMERICAN MUSEUM NOVITATES NO. 1761
Aperture broadly oval and auriculate, with a vertical axis. Peristome
wide, beveled, and much thickened inwardly. A carina of lesser or greater
prominence extends along the entire peristome. The thick inner terminus
is pressed downward over the open umbilicus. The base of the columella
is widely triangular, below the innermost portion of the peristome; the
latter is indented near its lowermost curvature. Parietal callus white,
opaque, and well developed; its thickened and slightly arcuate border is
continuous with the labial carina at its opposite ends. Parietal tooth low
and broad.
The color is uniform dull ochre-brown, excepting in one case where
it is deeper brown. The apex is not tinged with brown or purple-brown.
No banded shells were found.
AVERAGE MEASUREMENTS (15 MEASURABLE SHELLS): Shell length,
18.27 mm.; shell width, 11.99 mm.; shell proportions, 65.70 per cent;
aperture length, 10.11 mm.; aperture width, 8.23 mm.; aperture proportions,
81.30 per cent; proportions of aperture length to shell length, 55.30
per cent.
HABITAT: Uppermost portions of Voaara and Uparu valleys, Raiatea,
Society Islands. Terrestrial.
Unlike all the foregoing newly discovered species, representatives of
P. atilis have been known for some time, but hitherto they have not
been described or figured. Garrett collected the first specimens during his
earlier years of residence in the Society Islands and gave them the provisional
manuscript name of P. pinguis, although at a later time he
altered his view regarding their specific status. In his monograph (1884,
p. 77) he writes as follows: "My P. pinguis, of which I have seen only
a dozen examples, was found under decaying leaves in the mountain
ravines, at the head of Vaioara Valley. It certainly rustica." Incidentally,
the correct name of the locality is Voaara Valley (fig. 1). In his
chart that shows the distribution of the spepies of Partula of Raiatea,
published by Hartman (1881), Garrett correctly places this form under
the name of perpinguis-an orthography that occurs nowhere else in his
texts or in his correspondence. Hartman iticludes P. pinguis in his catalogue
(1881, p. 185) and comments as follows: "The form of the aperture
resembles P. rustica, but in size it approximates P. thalia. It is a
terrestrial species and probably P. rustica."
Owing to the lack of a description by Garrett or anyone else, and
also because the shells in question were regarded by Garrett and others
as variants of P. rustica, it is obvious that the early manuscript name is
a nomen nudum. The superseding name of P. atilis preserves the meaning
of Garrett's former designation.
1956 CRAMPTON: LAND SNAILS 15
The collections of P. atilis belonging to the present writer comprise
nine living animals and six dead shells from the inner portion of Garrett's
area, Voaara Valley, as well as three living specimens and one dead
shell from Uparu Valley that adjoins the former area on the south (fig.
1). The author's shells agree in all essential respects with the original
series of Garrett's so-called P. pinguis, of which seven have been located
and critically examined. Four specimens from Garrett's own collection
are now in the Bishop Museum of Honolulu, and their authenticity is
assured by the fact that they are labeled P. pinguis in Garrett's handwriting.
Three more of the original 12 are in the Hartman collection,
now deposited in the Carnegie Museum of Pittsburgh.
The shells of P. atilis differ so greatly from those of P. rustica as to
preclude the possibility that the two are one and the same species. The
former are larger in size and broader in shape. The spire is more stoutly
conical, and the whorls are more convex, in contrast with the flattened
contour of their homologues in P. rustica. The body whorl is more inflated.
The aperture of P. atilis is broad instead of narrow, and it is auriculate,
with an upper sinus that is disproportionately small. The lip is
massive and more incrassated within; its labial carina is more distinct
and prominent. Finally, a parietal tooth is present in all shells, whereas
it is very small or absent in P. rustica.
When the topic of the affiliations of P. atilis with other species of
Raiatea is finally considered, the judgment of the present writer is that it
belongs in the so-called "robusta group," of which the titular species exists
in abundance in the most northern portion of Raiatea and of which
the other members are found in neighboring valleys.
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