Micronesian Gastropods — Demond 
285 
Genus Tectus Montfort, 1810 
Tectus pyramis (Born, 1780) (syn. obeliscus 
Gmelin, 1791; acutus Lamarck, 1822; tabi- 
dus Reeve, 1861). 
Hirase and Taki (1951) pi. 65, fig. 8. 
Characteristically 2.5 to 3.5 inches long, 
white or grayish, and possessing a heavy, 
conspicuous columellar fold. 
Ordinarily found in rock crevices near the 
edge of seaward reef flats, both windward and 
leeward. Also taken on lagoon reef flats, on 
minor reef prominences in lagoons, and on 
coral masses in surge channels along the sea- 
ward reef edge. Lives at or near low tide line 
to depths of 10 feet. Commonly associated 
with species of Turbo , Vasum , and Bursa . 
GEOGRAPHIC range: Widespread and fairly 
common in Micronesia but not throughout 
the Indo-Pacific. Not found in Hawaii. US 
NM records are from southern Japan, the 
Ryukyu, Philippine, Mariana, Caroline, Mar- 
shall, Gilbert, Solomon, Loyalty and Fiji is- 
lands, Samoa, and New Caledonia. 
Genus Trochus Linne, 1758 
There are several closely related representa- 
tives of this genus in the Indo-Pacific. Ex- 
tensive study, beyond the scope of this paper, 
is needed to clarify their systematic positions. 
As in other groups, the most widely accepted 
and generally understood names are recorded 
here. 
Trochus histrio histrio Reeve, 1848. 
Typically 1 to 1.25 inches long, with a red 
columellar blotch and a spiral ridge within 
the columella. Characterized by beading of 
unequal size, the bead rows immediately above 
the sutures tending to be larger than the 
beading on the rest of the shell. The beading 
in general is finer than that of T. histrio in- 
t ext us} 
2 Unlike T. histrio histrio , the Hawaiian form of 
Trochus , T. histrio intextus Kiener (1850), possesses 
evenly spaced, spiral rows of uniformly sized beading 
over the entire shell. It lives among rocks of seaward 
reef flats. Morrison found specimens living on the 
concrete walls at Coconut Island, Kaneohe Bay, Oahu. 
Apparently it is limited to the Hawaiian Islands. 
Fig. 1 . Trochus histrio histrio Reeve. Bikini Atoll, 
Marshall Islands (USNM 579805). 
Commonly found on small reefs on lagoon 
floors in water 1 to 20 feet deep. Also lives 
on rocks in the lower intertidal zone of both 
windward and leeward ocean reef flats, ordi- 
narily on the reef edge. 
geographic range: Apparently limited to 
the Pacific. USNM collections are from the 
south China coast, southern Japan, and the 
Ryukyu, Philippine, Mariana, Palau, Caroline, 
Marshall, Gilbert, Ellice, and Line (Palmyra) 
islands. A common Micronesian species, not 
found in Hawaii. 
Trochus maculatus Linne, 1758. 
Hirase and Taki (1951) pi. 65, fig. 1. 
Characteristically 2 to 2.5 inches long and 
marked from apex to base with discontinuous 
longitudinal red streaks. T. maculatus lacks 
the columellar ridge and red columellar blotch 
of T. histrio. 
Lives on rocks at the outer edge of both 
seaward and lagoon reef flats. 
geographic range: USNM collections 
are from India, the Gulf of Siam, south China 
coast, southern Japan, from the Ryukyu, 
Palau, and Philippine islands, and from Arno 
Atoll. T. maculatus is rare in Micronesia, and 
absent from Hawaii, but it is fairly common 
in southern Japan and in the Ryukyu and 
Palau islands. 
Trochus niloticus Linne, 1767. 
Hirase and Taki (1951) pi. 65, fig. 6. 
