8 CLASS III. GASTEROPODA. ORDER II, CYCLOBRANCHIATA. 
the types of his grand primary division of the Mollusca ; this only shows 
the fallacious method to which that author was driven for classifying 
shells in the absence of their animal inhabitants. The respiratory organs 
of the cyclobranchiate Gasteropoda may be described as being of a some- 
what foliaceous or pyramidal form, symmetrical, more or less continuous, 
and placed around the body in a regular series under the edge of the 
mantle. The following three genera are referred to this order : 
CuiTon., 
CHITONELLUS. 
PATELLA. 
CHITON, Linneus. 
Testa ovalis, regularis, octovalvis ; valve transverse, convexe, in medio 
subrostrate, in serie unica ordinate ; superficie aut levi, aut imbri- 
cata, aut diverse striata ; marginibus dorsalibus valvarum incumben- 
tibus, invicem mobilibus ; lateribus cute cartilagini aut complanata 
aut coriaced aut spinosa aut hispida, validé infixis. 
The true characters of the Chitones, so far, at least, as regards their 
affinity with the Patelle, appear to have been first noticed by Adanson, 
an intelligent naturalist cotemporary with Linnzus; and it is certainly 
much to be regretted that the great author of the ‘Systema Nature’ 
should have been so strongly prejudiced in favour of his arbitrary divi- 
sion of univalves, bivalves, and multivalves, as not to have profited in many 
instances by the labours of this adventurous traveller in Senegal. Bru- 
guiére appears to have followed Linnzus, if we may judge by his arrange- 
ment of the figures in the ‘ Encyclopédie Méthodique ;’ but the anatomical 
investigations of Poli, Cuvier and Lamarck have singularly confirmed the 
anticipations of Adanson, though not without much hesitation on the 
part of the last-named author. De Blainville, as we have already no- 
