live, on wood
Siphonaria normalis Gould, 1846
|Maximum size: 20 mm shell
length (Kay, 1979).
shells of this species are limpet-like with white ribs and a
glossy-brown interior. Anterior and posterior ribs are similar in size
though the size of the ribs and the height of the shell vary greatly. (Note 1) Living animals are cream, mottled with gray and with yellow-white spots.
of Siphonaria normalis
are common in beach drift. Live animals are common in the high
intertidal on rocky coasts and occasional on overhanging kiawi branches.
Big Island, Maui, Oahu, Kauai and French Frigate Shoals (also Johnston Atoll?): widely distributed in the
Taxonomic notes: The fine-ribbed form of this species is listed separately in Severns (2011) as Siphonaria
sp. It's possible that there are more than one species. However,
considering the large number of intergrading populations (also noted by
Pilsbry in 1921), we've decided to leave it under Siphonaria normalis pending further work. Siphonaria amara (Nutatall MS) Reev, 1856 is a synonym. (Kay, 1979) It's referred to as the "false opihi" in Hoover, 1998 & 2006.
CP: intermediate ribs, largest 8 mm: composite photo, two shells;
beach drift, Maalaea Bay,
Maui; fall, 1979.
Observations and comments:
1: At any given site, the shells of
this species seem to be fairly uniform. However, at some sites they may
be flat and course ribbed, at others high and fine ribbed and at others
intermediate in both characters. As implied in the previous
sentence, the coarseness of the ribs and the height of the shell seem
to be correlated.