Land Snails of Ulithi Atoll — H arry 
213 
at least four species of ants, several kinds of 
flies, a small cockroach, a locust, several beetles, 
a butterfly, and a moth, as well as dermaptera, 
isoptera, and homoptera (one scale insect was 
very common). Most surprising was the pres- 
ence of mosquitoes and dragonflies, both of 
which require freshwater for the completion of 
their life cycles. There was also a small lizard 
(a skink) and one or more species of small 
forest birds. 
Of plants, there were several species of broad - 
leaf trees as well as pandanus and a few other 
shrubs. But, to a nonbotanist, these were eclipsed 
by the overwhelming abundance of the coconut 
palm. Contrary to popular opinion, the coco- 
nut palm, which is ubiquitous throughout the 
Pacific islands at lower elevations, does not con- 
stitute a natural forest. It is probably not even 
native to the area. The coconut groves are en- 
tirely the result of being planted and maintained 
(at least through replanting) by human agency. 
More detailed discussion of this subject will be 
found in Hedley (1899), O. F. Cooke (1910), 
Taylor (1950), Bates (1956), and Wiens 
( 1962 ) . From this it follows that the atolls 
forested with coconut palms are essentially cul- 
tivated areas. Wiens (1962) cites quite a few 
other plants which are introduced and main- 
tained by human agency on atolls. 
Some pertinent excerpts from Dr. C. M. 
Cookes letters to me follow: 
A number of genera [from Mogmog] such as Koro- 
ria, Nesopupa, Georissa, and Palaina are rarely, if 
ever, found on a typical atoll. From the list of the 
genera, the fauna appears to be that of a raised atoll 
such as Fais. I might hazard the guess that Ulithi is 
slightly raised with the islets composed of hard coral 
limestone. In typical, low lying atolls the interior of 
the islet is made up entirely of coral rubble. These 
typical atolls have a very restricted fauna made up 
mostly of species that are accidentally distributed by 
man. 
In 1941 we received a small collection from Fais. 
This island is east of Ulithi and about 65 feet high, 
with no lagoon. The genera and species of land shells 
coincide almost exactly with those we now know to 
inhabit Ulithi. Species from both these isalnds are 
quite distinct from those known to inhabit Yap. 
In my work on the faunas of the Pacific Islands I 
have divided the islands into three types. First, the 
high volcanic islands. Some of these may be quite old. 
The shell fauna of these islands contain endemic gen- 
era, subgenera and many species. Hawaii, Samoa, the 
Marianas, and all the important groups belong to 
this type. The lowland fauna may include many of the 
"wides” that are probably man-distributed. The sec- 
ond type is the raised coral island such as Fais in the 
Carolines; Makatea, Henderson, etc., in the Tuamotu. 
This type of island is not very old. They may have a 
few endemic species but not endemic genera. Quite 
a large portion of the fauna is man-distributed species. 
The third type of island is the low coral atoll. Some 
of these atolls may have as many as ten species but as 
the islands are apparently subjected to being washed 
over by hurricanes, all their shell species can be attrib- 
uted to man’s accidental introduction. 
The fauna of Ulithi falls in the second lot and that 
is why I hazard a guess that, near the center of each 
islet there should be a slightly raised coral reef rock. 
Dr. Cooke’s surmise that Mogmog represents 
an island of the intermediate type is evidently 
based on two facts: (1) the number of species 
of land snails is larger than is known from any 
other atoll, and (2) not all of these snails have 
as yet the notoriety of being tourist snails. The 
unusually large land snail fauna may be due in 
part to more deliberate and thorough collecting 
of Mogmog than other atolls have received. 
Some species have not previously been incrimi- 
nated as tourist snails, possibly because so little 
is known about them. Perhaps the richer fauna 
of Ulithi is only an indication of more frequent 
commerce than may occur at atolls with smaller 
snail faunas. 
The physical characteristics of Ulithi indi- 
cate that it is a typical atoll. Its slight elevation 
could have been the result of storm action. This 
is suggested by the small extent and location 
of the higher areas, as well as by the nature of 
the material — loose coral rubble — which pro- 
vided the higher ground. Rubble on the seaward 
edge of atolls seems to be a common phenome- 
non, caused by storm action (Hedley, 1896; 
Wiens, 1962). Wiens noted reports of a severe 
typhoon in 1906 which "almost destroyed" Uli- 
thi. Even if the elevation of Ulithi is due partly 
to regional uplift, as is probably the case at Fais, 
the land height at Ulithi would seem to be too 
slight to escape the ravages of complete but 
temporary submersion caused by the Pacific 
typhoons. 
Some of the snails of Mogmog are widely 
distributed in the Pacific and beyond, and have 
long been recognized as tourist snails. But of 
the rest, it is significant that the other localities 
from which they are known, the Palau Islands, 
