Barretthydrus is a genus of beetles in the family Dytiscidae, first described in 1927 by Arthur Mills Lea.Lea, A.M. 1927. On a new genus of water beetles (Dytiscidae). Records of the South Australian Museum (Adelaide) 3: 279-281 . The type species is Barretthydrus geminatus.
The genus is endemic to Australia, where it is found in New South Wales in the drainage basins of the Murray-Darling, and in coastal drainage basins, along the east coast from Queensland to Victoria.
The genus contains the following species:Dytiscidae Species List at Joel Hallan's Biology Catalog. Texas A&M University. Retrieved on 7 May 2012.
Barretthydrus geminatus Lea, 1927 Barretthydrus stepheni Watts, 1978 Barretthydrus tibialis Lea, 1927
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