Dear Conch-Lers,
 
The following observations are based primarily on my collecting in Florida,
with additional information provided by other collectors.
On the Gulf coast, two Neverita forms occur. Distinctions include habitat,
color, spire height, size and umbilical characteristics. While the two
forms are not often found together, one location at the mouth of Tampa Bay
has been found to be an overlap area. A number of specimens have been
collected there and photos of both kinds are now posted on the Jacksonville
Shell Club Home Page (http://home.sprynet.com/sprynet/wfrank/jacksonv.htm)
under Selected Past Newsletter Articles.
Neverita duplicata (Say, 1822) has a relatively squat and gray shell, often
reaching 60 mm. Some are considerably larger. The umbilical surface of the
body whorl is evenly rounded.
Neverita sp., as I'll call this form, has a relatively globose shell
tending toward brown in color. It seldom exceeds 45 mm. The umbilical
surface of the body whorl is strongly excavated. This channel within the
umbilicus is covered with a thick golden brown periostracum which
accentuates this striking feature.
Neverita sp. is common in bay and inlet areas of west Florida.
Neverita duplicata does not occur in estuarine habitats.Neverita duplicata
has been dredged offshore and collected on open beaches and at inlets on
both coasts of Florida.
The illustrations in Gould (1870) and Vokes & Vokes (1984), respectively,
suggest that Neverita duplicata ranges from Maine to Yucatan.
Specimens available to me indicate a range for Neverita sp. from Cape
Romano in Florida, northward and westward along the Gulf to at least
Gulfport, Mississippi.
I would be very interested in hearing from collectors of recent and fossil
forms in the southeastern U.S., who may have found this distinctive shell.
I'd better add one thing. I don't believe sexual dimorphism will explain
the differences. Long established populations on the west coast of Florida
thrive year after year with all members being of one form or the other.
Okay, let me have it!