Bolma
A genus of turban snails with a calcareous operculum and wide distribution.
Bolma is a genus of marine gastropod molluscs in the family Turbinidae—the turban snails. These medium to large sea snails have a calcareous operculum. The genus has a broad geographic range, occurring in the Red Sea, the Eastern Indian Ocean, the West Pacific, the South China Sea, the East China Sea, and off South Africa, Indo-China, the Philippines, Japan, Indonesia, New Caledonia, New Zealand, and Australia (New South Wales, Northern Territory, Queensland).
The fossil record of Bolma extends from the Eocene (about 33.9 million years ago) to the present. Fossil shells have been found in France, Greece, Japan, Morocco, Spain, Vanuatu, Guam, Cyprus, South Africa, Austria, Italy, Slovakia, New Zealand, Australia, and Tonga. Approximately five species are extinct.
The shell is imperforate and turbinate in shape, with a conic spire and whorls rounded at the periphery. Upper whorls are spiny, and the base of the shell is convex. The operculum is nearly round, with an excentric nucleus; its outer surface is polished, concave in the middle, with a convexity or rib at the center of the spiral. The radula’s central teeth lack cusps and have a narrow, long basal plate that extends above the tooth body. The tooth body is wide, oval, and not reflected above; its lower margin is not well-defined in the specimens examined. The lateral teeth bear cusps and are of the usual form.
Species included in the genus according to the World Register of Marine Species (WoRMS) and the Indo-Pacific Molluscan Database include *Bolma (Galeoastraea) asteriola* (Dall, 1925).
Quick Facts
- Taxon
- Bolma
- Type Species
- Bolma rugosa
- Type Species Authority
- Linnaeus, C., 1767
Facts from the source article.
Lore & Background
The genus Bolma is known from the Eocene to the Recent periods, with fossils found in locations including France, Greece, Japan, Morocco, Spain, Vanuatu, Guam, Cyprus, South Africa, Austria, Italy, Slovakia, New Zealand, Australia, and Tonga. There are about five extinct species. The shell is imperforate, turbinate in shape, with a conic spire and whorls rounded at the periphery; upper whorls are spiny, and the base is convex. The operculum is nearly round with an excentric nucleus, and the outside of the shell is polished, concave in the middle, with a convexity or rib upon the center of the spiral. The radula's central teeth have no cusps, with a narrow long basal plate produced above the body of the tooth; the latter is wide, oval, and not reflected above, with a lower margin not well-defined in the author's unstained specimens. The lateral teeth bear cusps.
Reader's Guide
Bolma is significant as a genus of marine gastropods within the family Turbinidae, characterized by a calcareous operculum and a fossil record extending from the Eocene to the present. Its wide modern distribution spans the Red Sea, Eastern Indian Ocean, West Pacific, South China Sea, East China Sea, and waters off South Africa, Indo-China, the Philippines, Japan, Indonesia, New Caledonia, New Zealand, and parts of Australia. The genus includes both extant and extinct species, with fossils recovered from numerous countries across Europe, Asia, Africa, Oceania, and the Pacific islands. The description of the radula and shell morphology, including the spiny upper whorls and polished operculum, provides taxonomic detail. The genus is listed in the World Register of Marine Species and the Indo-Pacific Molluscan Database, with species such as Bolma (Galeoastraea) asteriola included. The legacy of Bolma lies in its contribution to understanding turbinid snail evolution and biogeography, as documented in references from the late 19th century to the 21st century.
Did You Know?
- The genus Bolma has a fossil record from the Eocene to the Recent periods, spanning 33.9 to 0.0 million years ago.
- The central teeth of the radula in Bolma have no cusps.
- The operculum of Bolma is nearly round with an excentric nucleus.
Frequently Asked Questions
What is Bolma?
Bolma is a genus of medium-to-large marine gastropod molluscs placed in the turban snail family Turbinidae. A defining trait of the genus is the presence of a calcareous operculum, a hard plate that plugs the shell opening when the animal retracts.
Where can I find Bolma snails in the wild?
The genus enjoys a very broad tropical and subtropical distribution, ranging from the Red Sea and Eastern Indian Ocean across the West Pacific to the coasts of Japan, the Philippines, Indonesia, Australia, New Zealand, and New Caledonia. Populations are also recorded off South Africa, Indo-China, and in the South and East China Seas.
How far back does the Bolma fossil record extend?
Fossil shells identified as Bolma reach back to the Eocene, roughly 33.9 million years ago, and the lineage continues to the present. Remains have been recovered from deposits in France, Spain, Italy, Greece, Morocco, Japan, New Zealand, Australia, and several Pacific island nations.
What sets Bolma apart from other members of Turbinidae?
Beyond the shared globose shell shape typical of turban snails, Bolma is noted for its calcareous operculum and its generally medium-to-large body size. The genus also spans a wider geographic footprint than many of its close relatives within the family.
Are there any extinct Bolma species?
Roughly five species within the genus are known exclusively from the fossil record and are regarded as extinct. Their shells have been identified in Eocene and younger sediments across Europe, North Africa, and parts of the Pacific.
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