18 
terrestiual molltjsca inhabiting society 
ISLANDS. 
.synonymous species. Several years axucx ^ number of new 
States Exploring Expedition, commanded by Capt. Wilkes, collected a number ol ne 
species, all of small size, wliicli were described by Dr. Gould in t le “ 
the lioston Society of Natural Hletory and subeoquoutly 
and hgurod in tlio official work, “Mollusca and .Sliclls.” In 1864, MM. Ilomb.on .u d 
Jacquinot (Voy. Pol Sud), described two new species and added a spronym to 
Gould’s nelix CrMa, two to Pfeiffer’s Helix eoarctata, and one to Goidd^^s HeUx 
hursatella. In 1867, Johann Zelebor, one of the naturalists of the “>ovara 
expedition round the world in 1857 to 1859, described Piqm hyalina (= Vertigo 
pediculns). Pupa Dunlceri (= Vertigo tantilla), and Hydrocena Scherzeri, all found on 
Taliiti ; tlie last probably equals one of the extreme forms of the variable Omphalo- 
tropis 8citula. 
During the years 1860 to 1863, I made a much more thorough exploration than 
any of my predecessors, and, by searching in nearly every valley in the group, dis- 
covered over 50 new species. Most of these were described by the late Mr. . 11. 
I’ease in the “ Proceedings of the Zoological Society,” and in the “American Journal 
of Conchology.” The other species with his MS. names have been freely distributed, 
and tlie majority recorded in catalogues. All of these are for the first time described 
in the following pages. Since my residence in the group, from 1870 up to tlie present 
time, I have continued my researches, and added 19 new species to the list, one of 
which, Partula acuticosta, Mousson, MS., is recorded in “Museum. Godeffroy Catal., v,” 
and one, Parhda Mooreana, Hartman, is described in the “ Proceedings of the 
Academy of Natural Sciences of Philadelphia.” 
Genus MICROCYSTIS, Beck. 
I restrict this genus to a group of small Helices, Avhich are characterized by their 
orbicular, more or less depressed form, rounded, angulate or subangulatc periphery, 
and smooth, shining surface. The umbilicus, though usually closed, is occasionally 
minutely perforated, llic peristome is straight and sharp, with remote margins. 
The columella is simple, or callous, and frequently armed with a nodule or slightly 
t\\ isted plait. In color they vary from whitish corneous, through all the intermediate 
tints, to fulvous ; rarely ornamented with bands and spots. One species only exhibits 
a sculptured surface. 
They are widely diffused throughout Polynesia, ranging from the lowlands near 
the seashore to several thousand feet above sea-level. A majority of the species are 
strictly terrestrial, and delight in moist stations, hiding beneath decaying leaves, under 
rotten ivood and among loose stones. Others are entirely arboreal, on the foliage of 
shrubs and ferns. A number of the species are gregarious. 
