Actinocyclus 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 slug

Slug

Slug is a common name that is normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell...

s, dorid nudibranch

Nudibranch

A nudibranch is a member of what is now a taxonomic clade, and what was previously a suborder, of soft-bodied, marine gastropod mollusks which shed their shell after their larval stage. They are noted for their often extraordinary colors and striking forms...

s, shell-less 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 Actinocyclidae

Actinocyclidae

Actinocyclidae is a family of sea slugs, dorid nudibranchs, marine gastropod mollusks in the superfamily Doridoidea. This family is within the clade Euctenidiacea.-Taxonomy :Genera within the family Actinocyclidae include:...

.

This genus is not to be confused with Actinocyclus  Ehrenberg, 1837 , a genus of diatom

Diatom

Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...

s in the family Hemidiscaceae.

Species

Species in the genus Actinocyclus include:

• Actinocyclus laevis (Bergh) (synonym of A. verrucosus)
• Actinocyclus japonicus Eliot, 1913 (synonym of A. verrucosus)
• Actinocyclus papillatus Bergh
  Rudolph Bergh
  Rudolph Bergh , full name Ludvig Sophus Rudolph Bergh, was a Danish physician and malacologist. He worked in Copenhagen....
  
  , 1878
• Actinocyclus verrucosus Ehrenberg
  Christian Gottfried Ehrenberg
  Christian Gottfried Ehrenberg , German naturalist, zoologist, comparative anatomist, geologist, and microscopist, was one of the most famous and productive scientists of his time.- Early collections :...
  
  , 1831

However, A.Valdés in his "Review of the genus Actinocyclus" (2002) contends that there are only two species in this genus :

• Actinocyclus papillatus Bergh
  Rudolph Bergh
  Rudolph Bergh , full name Ludvig Sophus Rudolph Bergh, was a Danish physician and malacologist. He worked in Copenhagen....
  
  , 1878
• Actinocyclus verrucosus Ehrenberg
  Christian Gottfried Ehrenberg
  Christian Gottfried Ehrenberg , German naturalist, zoologist, comparative anatomist, geologist, and microscopist, was one of the most famous and productive scientists of his time.- Early collections :...
  
  , 1831

According to him, other species described in this genus are either junior synonyms or belong to other genera.