Umbonium, sometimes known as "button top shells", is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of sea snail

Sea snail

Sea snail is a common name for those snails that normally live in saltwater, marine gastropod molluscs....

s, marine

Marine (ocean)

Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...

 gastropod molluscs in the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Trochidae

Trochidae

The Trochidae, common name top snails, are a taxonomic family of very small to large sea snails, marine gastropod molluscs in the clade Vetigastropoda ....

, the top snails.

Shell description

The shells of the species in this genus are low-spire

Spire (mollusc)

A spire is a descriptive term for part of the coiled shell of mollusks. The word is a convenient aid in describing shells, but it does not refer to a very precise part of shell anatomy: the spire consists of all of the whorls except for the body whorl...

d and shaped like a button, and the umbilicus of the shell is often completely covered with a thick and smooth callus.

Species

Species in the genus Umbonium include:

• Umbonium callosum Sowerby
• Umbonium capillata A. A. Gould, 1861
• Umbonium conicum (A. Adams
  Arthur Adams (zoologist)
  Arthur Adams was an English physician and naturalist.Adams was assistant surgeon on board H.M.S. "Actaeon" in company with HMS Samarang in the British Navy during the survey of the Malay Archipelago, the Japan Sea, Korea and China,from 1843 to 1846. He edited the Zoology of the voyage of H.M.S....
  
   & Reeve
  Lovell Augustus Reeve
  Lovell Augustus Reeve was an English conchologist.Lovell Augustus Reeve was initially apprenticed to a grocer of Ludgate Hill between 1827 and '34...
  
  , 1850)
• Umbonium costatum (Valenciennes
  Achille Valenciennes
  Achille Valenciennes was a French zoologist.Valenciennes was born in Paris, and studied under Georges Cuvier. Valenciennes' study of parasitic worms in humans made an important contribution to the study of parasitology...
  
   in Kiener, 1838 in 1834-50)
• Umbonium elegans (Kiener, 1838)
• Umbonium eloiseae Dance, Moolenbeek & Dekker, 1992
• Umbonium fenestrata T. Kuroda,
• Umbonium floccata G. B. Sowerby III, 1903
• Umbonium giganteum
  Umbonium giganteum
  Umbonium giganteum is a species of sea snail, a marine gastropod mollusk in the family Trochidae, the top snails....
  
  (Lesson, 1833 in 1832-35)
• Umbonium guamensis J. R. C. Quoy & J. P. Gaimard, 1834
  • Umbonium guamensis selenomphala H. A. Pilsbry, 1905
• Umbonium moniliferum
  Umbonium moniliferum
  Umbonium moniliferum is a species of sea snail, a marine gastropod mollusk in the family Trochidae, the top snails....
  
  (Lamarck, 1822 in 1815-22)
• Umbonium nitida A. Adams, 1863
• Umbonium omphalotropis A. Adams, 1863
• Umbonium polita A. Adams, 1862
• Umbonium pulchella A. Adams in H. & A. Adams, 1854
• Umbonium roseopunctata T. Kuroda & T. Kinoshita
• Umbonium rufula A. A. Gould, 1861
• Umbonium sagittata (Hinds, 1845)
• Umbonium sanguinea H. A. Pilsbry, 1905
• Umbonium suturale (Lamarck, 1822 in 1815-22)
• Umbonium thomasi
  Umbonium thomasi
  Umbonium thomasi is a species of sea snail, a marine gastropod mollusk in the family Trochidae, the top snails....
  
  (Crosse, 1862-a)
• Umbonium vestiarium
  Umbonium vestiarium
  Umbonium vestiarium, common name the button tops, is a species of sea snail, a marine gastropod mollusk in the family Trochidae, the top snails....
  
  (Linnaeus, 1758)
• Umbonium vestiarium
  Umbonium vestiarium
  Umbonium vestiarium, common name the button tops, is a species of sea snail, a marine gastropod mollusk in the family Trochidae, the top snails....
  
  (Linnaeus, 1758)
• Umbonium zelandica
  Umbonium zelandica
  Umbonium zelandica, common name wheel shell, is a species of small sea snail, a marine gastropod mollusc in the family Trochidae, the top snails.thumb|left|200px|Umbonium zelandica underside view-References:...
  
  (Hombron & Jacquinot,1855)