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divisions into which the Aquatic Beetles may be 

 divided ; namely, the Hydradephaga of MacLeay, 

 and the Rypophaga of Stephens. The Gyronecha 

 of Kirby, comprising under that denomination the 

 Whirl Beetles, or Waltzing Beetles, (Gyrinidse, 

 Leach) appear to be altogether a distinct group, 

 and will be treated as such ; instead of therefore 

 dilating at present on the Aquatics generally, it 

 will be better to remark on them separately as they 

 occur in the respective works of Linneus and 

 Fabricius, merely premising that out of twenty- 

 three species published by the former writer, under 

 the term of Dytiscus, these have been subdivided 

 by later authors into fifteen genera. 



Dytiscus, Linneus. 



Sp. 1. Piceus. — Now an Hydrous of Leach, 

 and of the family of the Hydrophilidse of the same 

 Author ; the following genera belong to it, viz. 



