He differs from Cuvier in regarding the tunic as the homologue of the shell of Lamellibranches, remarking that it differs in being muscular and contractile.
Lamarck's fame as a zooelogist rests chiefly on this great work.

It elicited the highest praise from his contemporaries.

Besides containing the innovations made in the classification of the animal kingdom, which he had published in previous works, it was a summary of all which was then known of the invertebrate classes, thus forming a most convenient hand-book, since it mentioned all the known genera and all the known species except those of the insects, of which only the types are mentioned.

It passed through two editions, and still is not without value to the working systematist.
In his _Histoire des Progres des Sciences naturelles_ Cuvier does it justice.

Referring to the earlier volume, he states that "it has extended immensely the knowledge, especially by a new distribution, of the shelled molluscs ...