Micronesian Gastropods — Demond 
313 
Has also been taken, though uncommonly, 
from small reefs on lagoon floors. 
geographic range: USNM records are 
from South Africa and Mauritius eastward 
through the Indian and Pacific oceans to the 
Tuamotu and Society islands and to Clipper- 
ton Island in the eastern Pacific, and also from 
the Ryukyu and Hawaiian islands south to the 
East Indies and Fiji. Reported from northern 
Australia. Common in Micronesia. 
Genus Maculotriton Dali, 1904 
Maculotriton digitalis (Reeve, 1844). 
Fig. 21. Maculotriton digitalis (Reeve). Ifaluk Atoll, 
Gilbert Islands (USNM 614193). 
Characteristically about one-half inch long. 
Sculptured with spiral cords and low, broad 
transverse ribs. Whitish in color with a spiral 
pattern of yellowish or chestnut-brown spots, 
which is frequently obscured. 
Ordinarily found under rocks and in tide 
pools on windward ocean reef flats. 
geographic range: Apparently limited to 
the Pacific. USNM records are from southern 
Japan, the Bonin, Caroline, Marshall, Gilbert, 
Hawaiian, Line, Society, and Tuamotu is- 
lands. Reported from northeastern Australia. 
Uncommon in Micronesia. 
Genus Thais Roding, 1798 
Thais armigera (Link, 1807). 
Hirase and Taki (1951) pi. 110, fig. 2; 
Tinker (1952) p. 98, 4 figs, on p. 99 
[as T. affinis Reeve]. 
Characteristically about three inches long 
and whitish with a yellowish-pink aperture. 
Ordinarily found clinging to rocks of wind- 
ward ocean reef flats, just shoreward of the 
reef edge. Also occurs along windward lagoon 
margins of broad atolls where the lagoon reef 
flat exhibits features of a seaward reef. In- 
variably found in shallow water, either just 
below low tide line or in reef flat tide pools. 
Commonly so thickly encrusted with coral- 
line algae, Foraminifera, vermetids, and Hip- 
ponix it is difficult to distinguish from the reef 
surface. 
GEOGRAPHIC range: USNM records are 
from Mauritius and Cocos-Keeling Atoll in 
the Indian Ocean eastward through the Pacific 
to the Society and Tuamotu islands, and from 
southern Japan south to the Solomon Islands 
and New Caledonia. Reported from northern 
Australia and Hawaii. Fairly common in Mi- 
cronesia. 
Thais hippocastanum (Linne, 1758) (syn. acu- 
leata Deshay es, 1844; pseudohippocastanum 
Dautzenberg, 1929). 
Fig. 22. Thais hippocastanum (Linne). Kwajalein 
Atoll, Marshall Islands (USNM 607586). 
Characteristically 1.5 to 2.5 inches long. 
Resembles T. tuherosa in its shape, knobby 
surface, and yellowish-white aperture. How- 
ever, unlike T. tuherosa , the brown color on 
its outer lip extends into the aperture as spiral 
bands, and the brown color on its columella 
is diffused instead of in distinct spots. 
Ordinarily lives among rocks and in sandy- 
rocky tide pools on seaward reef flats, both 
windward and leeward. Occurs across the reef 
from near low tide line to the upper intertidal 
zone. Also found, though infrequently, on 
lagoon reef flats. Specimens are often heavily 
encrusted and appear to be part of the reef 
surface. 
GEOGRAPHIC range: USNM records are 
from the east coast of Africa eastward through 
