526 HISTORY OF SYSTEMS. 



** Bivalve, the valves unequal. Gen. : Acardium, Ra- 

 diolites, Cama, Spondylus, Plicatula, Gryphaea, 

 Ostrea, Vulsella, Malleus, Avicula, Perna, Placuna, 

 Pecten, Lima, Pedum, Pandora, Corbula, Anomia, 

 Crania, Terebratula, Calceola, Hyalaea, Orbicula, 

 Lingula. 



*** Multivalve and no hinge. Gen. : Anatifa, Balanus. 

 This arrangement is inferior to the previous one of Cuvier 

 in several respects ; but the division of the Mollusca into 

 two primary sections from the character of the head, is both 

 convenient and physiologically correct, for it indicates cor- 

 responding modifications in the development of the nervous 

 system. External habit likewise proves the value of the 

 division. There is a wide difference in the physiognomy 

 of a naked cephalous mollusk, and in that of a naked ace- 

 phalous one, marking indisputably the superior faculties and 

 structure of the former; and the shell of the testaceous 

 mollusk that is headed is univalve or imbricate, while that 

 of the acephala is uniformly bivalvular. But the chief merit 

 of this artificial method is the creation of many new genera. 

 Bruguiere had proposed sixty-one genera ; Lamarck here 

 raised the number to 126 ; and so well were they limited and 

 true in nature, that they have been all retained in the most 

 approved systems that followed. 



But Cuvier was the moving spirit that led to every useful 

 reform. In a series of admirable essays published in the 

 " Memoires du Museum," * he skilfully developed the ana- 

 tomy of the principal genera of the Mollusca, and rendered 

 his descriptive details interesting by the ease and perspicuity 

 of his style, by his mastery of his subject and over all that 

 had been done before him, and by his critical acumen in 

 questionable points. His eloquent lectures told more imme- 

 diately on his pupils, who arose around the great master in 

 zealous numbers ; and to two of them we are indebted for 

 the publication of those lectures, which to this day declare 

 the solidity of the fame they had so early procured him. In 

 the volume published in 1800 there is the following synopsis 

 of his method of classifying the Mollusca at that period : 



* Subsequently collected together, and published in a quarto volume, with 

 the title " Me'moires pour servir a 1'histoire et a 1'anatomie des Mollusques, 

 par M. le Chevalier Cuvier." Paris, 1817. It is essential to the library of 

 the Conchologist. 



