Arionellus
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Arionellus Barrande, 1850, is a disused name for a genus of trilobite. The name Arionellus was a replacement for Arionides Barrande, 1847, itself a replacement for Arion Barrande, 1846, which was preoccupied because Férussac had already used it in 1819 for a genus of slugs.
Agraulos had already been proposed as replacement for Arion by Hawle and Corda in 1847, but Barrande unjustly considered it a homonym of Agraulis, a butterfly named by Boisduval in 1836.{{cite journal|first1= F.B.|last1= Meek|first2= F.V.|last2= Hayden|year= 1865|title= Palaeontology of the upper Missouri – A Report upon Collections made principally by the Expeditions under command of Lieut. G.K. Warren, U.S. Top. Egrs. in 1855 and 1856 – Invertebrates, Part I|journal= Smithsonian Contributions to Knowledge|volume= 14|issue= 1|pages=7–8|url= https://books.google.com/books?id=ki5DAQAAIAAJ&pg=RA3-PA8 }}
The species of Arionellus have now been reassigned to the following genera.{{cite book|last= Moore|first= R.C.|year= 1959|title= Arthropoda I - Arthropoda General Features, Proarthropoda, Euarthropoda General Features, Trilobitomorpha|publisher= Geological Society of America/University of Kansas Press|series= Treatise on Invertebrate Paleontology|volume= Part O.|pages= O207, O250, O256, O272, O278, O298, O306, O322|location= Boulder, Colorado/Lawrence, Kansas|isbn= 0-8137-3015-5}}
- A. bipunctatus = Croixana bipunctata
- A. ceticephalus = Agraulos ceticephalus
- A. convexus = Camaraspis convexa
- A. cylindricus = Keithiella cylindrica
- A. oweni = Modocia oweni
- A. primaevus = Strenuaeva primaeva
- A. pustulatus = Glaphurus pustulatus
- A. texanus = Tricrepicephalus texanus
- A. tripunctatus = Tricrepicephalus tripunctatus