LAMARCK. 



About the year 1787, in the Nova Testaceorum Genera*, 

 Retzius proposes to add three genera to the Linnaean ones, 

 which is stated to be according to the intentions of Linnaeus, 

 as communicated to him by Achariusf : 1st, Perna, which in- 

 chides Mya Perna and some species of Mi/tUus ; 2dly, Unio, 

 consisting oi'Mi/a Pictorum and margaritifera ; and 3dly, Me- 

 liiia, of Ostrea seini-aiirita, Perna Isogonum, and Ephippium. 

 He also proposes to di\ ide the genus Anomia into fovu', viz. 

 Anomia, Crania, TerebratuUi, and Placenta. Most of these 

 genera liave since been adopted by M. Lamarck. 



Considering the number of shells that have been already col- 

 lected fi'om all parts of the world, and which have not yet found 

 their proper places in the system, from their not perfectly agree- 

 ing with any of tlie genera already established, the necessity 

 of improving the Linnaean system, by increasing the number 

 of genera and rendering them more definite, becomes every 

 day more apparent. Something of tliis sort has been lately 

 attempted in France by M. Lamarck (who enjoys the advan- 

 tage of free access to the National Museum of Natural History 

 at Paris) in his Systeme des Animaux sans Vertebres, and in 

 his other writings. 



M. Lamarck's arrangement has been followed in this coun- 

 try by Mr. Parkinson, in his description of fossil shells, in 

 the third volume of Organic Remains of a Former World, in 



* Linn. Trans, vol. 7. p. 204. t Ibid. 



