42 MOLLUSCA. 
species of the genus Lepas of Linnzeus. The shells belong- 
ing to the Linnzan genera Sarpula and Dentalium, are 
transferred to the class termed Annelides. 
This system of the molluscous animals is unquestionably 
the most perfect of all those which have been published. 
But, with all its excellence, we must inform the reader, 
that many species, nay, whole genera, have their places as- 
signed them in this natural method, merely because the 
shells occupied a similar position in the artificial system, the 
form of the inhabitants being unknown. 
Section [V.— Mixed Systems. 
In this section, we shall confine our remarks to the only 
system of this kind of any consequence which has hitherto 
appeared, and which is the production of the late industrious 
Lamark, one of the most celebrated zoologists of the French 
school. The Systeme des Animaux sans Vertebres, Paris, 
1801, of this author, embraces the whole range of animals in- 
cluded in the classes Insecta and Vermes of Linnzeus. Where 
treating of the Mollusca he divides them into two orders. 
The first, termed Cephalous, from possessing a head, in- 
cludes the univalves. The second, termed Acephalous, from 
the absence of a head, includes the bivalves. This eminent 
author greatly modified his views, as appears from what he 
announced in his Extrait du Cours de Zoologie, Paris, 1812, 
the prelude to his last and great work, Histoire Naturelle 
des Animaux sans Vertebres, the fifth, sixth, and seventh vo- 
lumes of which refer to the Mollusca, he fortunately lived to 
finish between the years 1818 and 1822. The arrangement 
adopted in this invaluable work, has been greatly admired, 
a circumstance which induces us to give the following sy- 
noptical view of its contents. 
