Micronesian Reef-associated Gastropods 
Joan Demond 1 
This report is a synopsis of existing 
knowledge of the ecology and zoogeography 
of Micronesian reef-associated gastropods. It 
summarizes for each species the environmental 
conditions in which living specimens have 
been found, and it outlines the recent geo- 
graphic occurrence of each species through- 
out the entire Indo- Pacific region (see Plate 4). 
Brief descriptions of the shells, with illustra- 
tions of some of them and reference to pub- 
lished figures for all of them, are also included. 
The report is intended both as an aid to re- 
search by others and as a guide for future 
collectors. It is based mainly on the notes and 
collections of field parties whose work in 
Micronesia since 1945 has increased both the 
data and the demand for such a summary. 
The fact that a similar study has not been 
made before reflects, perhaps, the paucity of 
ecologic data in previous collections. Indeed, 
the extensive Indo-Pacific mollusk collection 
in the U. S. National Museum, which so sub- 
stantially supplemented the zoogeographic 
and systematic parts of this paper, is almost 
devoid of ecologic records for specimens col- 
lected earlier than about 1945. 
The information summarized here is surely 
not the complete or final story for the gastro- 
pods. Originally it was hoped to include the 
pelecypods as well, and, in addition, to at- 
tempt a more comprehensive general analysis 
of the whole group; but time did not permit 
such a complete study, and it is hoped that 
these aspects of the gastropods will be cov- 
ered in later publications. 
1 Research Associate, Department of Geology, Uni- 
versity of California at Los Angeles, Los Angeles, 
California. Manuscript received January 31, 1956. 
SOURCES OF DATA 
The ecologic data on which this study is 
based are taken from eight collections of 
mollusks made in Micronesia since 1944, 
comprising about 12,000 lots and over 200,000 
specimens. The collections are from Onotoa 
Atoll in the Gilbert Islands, from Saipan in 
the Mariana Islands, from Yap and Ifaluk in 
the West Caroline Islands, and from Bikini, 
Eniwetok, Rongerik, Rongelap, Arno, and 
Majuro atolls in the Marshall Islands. All of 
these islands lie within the geographic area 
of Micronesia, as outlined in Plate 4. De- 
tails regarding principal collectors, sponsor- 
ing organizations, size of collections, and 
dates of field studies are given in Table 1. 
These collections have been added to those 
in the U. S. National Museum. 
Geographic distribution data, shell meas- 
urements and descriptions, and estimates of 
relative abundance are based on the entire 
Indo-Pacific collection in the U. S. National 
Museum. 
Supplementary information, zoogeo- 
graphic, systematic, and ecologic, has been 
obtained from published records and from 
personal communications. For the ecologic 
summaries, unless otherwise specified, only 
data referring to specimens taken alive or 
obviously recently dead were accepted, in 
order to be reasonably sure that the species 
actually lived in the environment described 
for them. 
ACKNOWLEDGMENTS 
So many people have contributed to this 
study in one way or another that it is im- 
possible to list them all. Thanks go to every- 
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