Micronesian Gastropods — Demond 
279 
undata , Monodonta labio) imply that these spe- 
cies live only on a muddy substrate such as 
that found adjacent to high, volcanic islands 
and continental shores, and that they are not 
found on the limesand substrate of atolls (or 
similar parts of other shallow tropic seas). 
The fact that most species are recorded equally 
from atolls, high islands, and along conti- 
nental shores suggests that most of the col- 
lections studied are taken from reefs or 
reef-associated limesands and not from sites 
strongly influenced by volcanic or terrestrial 
sedimentation. 
SYSTEMATIC ANALYSES 
Procedures 
Only gastropods in the recent Micronesian 
collections mentioned are considered in this 
study. They number 175 species, grouped in 
53 genera, and representing 25 families. Be- 
cause of collecting areas and methods, they 
are almost exclusively shallow-water forms, 
which live on or in close association with 
reefs. The summary provided for each species 
includes the name apparently regarded as 
most acceptable by practicing specialists, ref- 
erence to a convenient published illustration 
or a drawing made especially for the present 
work, a brief description of the shell, its 
ecology as presently understood, its geo- 
graphic range in the Indo-Pacific, and its 
abundance in Micronesia. 
Taxonomic Arrangement 
The brief descriptive notes are intended 
purely as a field aid to species recognition and 
not as definitive descriptions or revisions. 
This is not a taxonomic paper. In general, 
the systematic arrangement of families and 
genera is according to Thiele (1929 and 1931). 
Species are listed alphabetically under each 
genus. For species which have commonly 
been recognized by several names, their well- 
known synonyms are listed parenthetically. 
The Mitridae are arranged after Dautzenberg 
(1935), and the Cypraeidae, for the most part, 
after Schilder (1938). In some instances, where 
previous authors have subdivided families 
into many genera which have not gained com- 
plete acceptance, those genera are used here 
as subgenera. For instance, in the Cypraeidae 
the generic name Cypraea is used throughout, 
whereas the generic names of Schilder (1938) 
are included as subgenera. In other groups, 
such as the Conidae and Terebridae, sub- 
generic names are excluded entirely. 
Shell Illustration and Description 
As far as possible, reference to a good illus- 
tration of each species is provided. Such ref- 
erences are to readily available texts, most 
frequently to A Handbook of Illustrated Shells 
by Hirase and Taki (1951), Pacific Sea Shells 
by Tinker (1952), A Field Guide to Shells of the 
Pacific Coast and Hawaii by Morris (1952), 
and to Coloured Illustrations of the Shells of Japan 
by Kira (1955). In a few instances reference 
is made to "Shells Take You over World 
Horizons," an article by Platt in the National 
Geographic Magazine (July, 1949). 
When an accurate illustration is not avail- 
able in a convenient reference, pen and ink 
drawings prepared by Carolyn Bartlett of the 
U. S. Geological Survey are furnished. Forty- 
two species are thus illustrated with original 
drawings; most of these species appear to 
have been rarely collected although some of 
them are common or even very common in 
Micronesia. In these original drawings, the 
scale marks beside the figures represent one 
centimeter. 
These illustration references and original 
pen and ink drawings are supplemented by 
brief descriptions of the shells. For each spe- 
cies, a characteristic shell length is given. In 
most instances, shell color is noted, particu- 
larly if the illustration is in black and white. 
Obvious sculptural features are also men- 
tioned. For species which are commonly con- 
fused with other species, distinguishing char- 
acteristics are noted. 
Ecologic Summaries 
The ecology of each species is compiled 
from data accompanying the eight Microne- 
