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finding the Patella anomala'm Miiller's Zoologia Danica and not recog- 

 nizing their identity, though he appears to have observed a degree of 

 resemblance, he seems to have founded his genus Orbicula partly upon 

 Miillers plate and partly upon some recent specimens of a very different 

 thing which existed in the collections at Paris at the time. Miiller's 

 Patella anomala is however absolutely identical with the Crania 

 Personata, consequently Lamarck's genus Orbicula must be entirely 

 abandoned unless it can be used as applied to that other very different 

 thing which Lamarck had under his observation at the same time 

 and which he did not distinguish fron) Miiller's Patella ; and this is 

 what I think ought to be done. But this is not the end of the confusion 

 caused by Lamarck's inattention ; for upon receiving from my Father 

 some specimens of a small attached bivalve which I found among some 

 Ballast, and not identifying them with the other similar things which he 

 had before considered as identical with Miiller's Patella anomala, he has 

 put these into another place in his Systeme, under the name of DisciNA 

 ostreoides. Thus his genus Orbicula has been formed in a great measure 

 upon a shell which is identical with his Crania, but separated from it by 

 being placed among the Brachiopodes, while Crania stands in the Rudis- 

 tes ; and his genus Discina has been made out of another thing which 

 properly belongs to Orbicula, but separated from it by being placed 

 among the Rudistcs, while Orbicula stands among the Brachiopodes. 

 Lamarck should also have referred Poli's Anomia turbinata to Crania 

 and not to Orbicula. 



I mutt now acknowledge my own errors, which have, however, princi- 

 pally, if not entirely been caused by my placing implicit confidence 

 in the correctness of Lamarck. The first and leading error of which I 

 have been guilty is that of having adopted Lamarck's incorrect notion by 

 supposing the Patella anomala of Miiller to be distinct from Crania 

 and regarding it as forming the typical species of Orbicula ; my next 

 error has been that of identifying the shell I found among Ballast with 

 Orbicula norvegica of Lamarck whereas it ought to have been placed 

 as a new species of that genus. These errors of mine appeared first in 

 the Linn. Trans, and they have been continued in my work on the Genera. 



