ANCYLUS. 



tlie analogous position of its several parts with those o 

 other univalves from which it principally differs in want- 

 ing spiral volutions. Aperture oval or oblongs with very 

 entire edges. 



Of this Genus two species only are known which are 

 the Patell(E lacustris and jhwiatilis of Linn., one of whic 

 has an oval and transverse aperture, and the other, whei 

 placed in a similar position, an oblong and longitudina 

 aperture. Both are common in this country. Drapar 

 naud describes a third species under the name of Ancylu 

 spina-ros<T, which, however, has been most satisfactoril 

 proved by M. De Ferussac to belong to a Linnean Mono 

 cuius, one of the Crustaces Branchiopodes frangts of La 

 march, which is furnished with two equal valves that ope 

 and shut like a little muscle ; and we regret to find that 

 since this has been made known, Lamarck should hav 

 inadvertently continued Draparnaud's mistake. 



Not known in a fossil state. 



