CHAPTER IL 
COLLECTIONS FROM GUAM AND SAIPAN. 
ENDEMIC SPECIES OF PARTULA. 
The Mariana Islands are inhabited by four species of the genus which occur 
nowhere else, in full accordance with the principle that each group of islands pos- 
sesses its own characteristic forms; the previously known species are regarded by 
Pilsbry as sufficiently distinctive to justify their assignment to a_ separate 
section of the genus, MarIANELLA. Only the southern islands are ecologically suit- 
able and, as the preceding chapter has shown, only certain portions of these islands 
are possible as habitations. The northern members of the group are relatively 
recent in their construction by volcanic agencies, and they are devoid of large land 
snails. 
Prior to 1819 no Partule were reported by the scientific expeditions to the 
Ladrones.1 In the year specified, the Uranie visited the islands, bearing the 
members of the de Freycinet expedition, among whom were the botanist Gaudi- 
chaud-Beaupré and the zoologists Quoy and Gaimard. 
Partula gibba Férussac (1821) was collected by this expedition, and it is the 
most important among the Mariana species for the reason that it inhabits Tinian 
and Saipan as well as the larger island of Guam; it is not known whether it also 
occurs on Rota. A second species, P. fragilis Férussac (1821), is undoubtedly 
another discovery of the same expedition, for it is equally old in the literature; the 
describer gave no figures of the shell, and the species remained “lost” for decades. 
This is the form that was rediscovered by Quadras and it was described as P. 
quadrasi in 1894 by von Moellendorf, who, like Férussac, failed to give illustrations 
of his material. The observations of the present writer leave no doubt that the two 
authors had the same species in hand, and that therefore the older name must stand. 
The species inhabits Guam only, so far as is known, and it exists locally in that 
island. Partula radiolata Pfeiffer (1846) is next in seniority; it is not recorded 
outside of Guam, where it occurs in smaller numbers than P. gibba, and it is slightly 
less ubiquitous. Partula salifana is the fourth species, and it is a new discovery; it 
was found on the high vegetation near the summit of Mount Salifan—a somewhat 
remote peak in the southwestern part of Guam. In its isolation it is like P. filosa, 
which occurs in a portion of a single valley in the one island of Tahiti. From the 
foregoing review, it is clear that each species presents features of peculiar individual 
and comparative interest; each will be treated in a separate chapter, with the excep- 
tion that P. gibba requires an independent analysis of its representatives in Guam 
and in Saipan. 
AREAS OF COLLECTION IN GUAM. 
A fundamental task of the present investigation is the exact determination of 
the places where distinguishable species and varieties existed at the time of the 
field-studies. From such basic facts of distribution, conclusions are hereinafter 
1 An account of the early scientific exploration of the Mariana Islands is given by Safford, loc, cit., pp. 12-41. 
19 
