156 THE HISTORY OF CREATION. 
perfect forms) to be morphologically the lowest among the 
four higher tribes of animals. 
Whilst, for reasons already given, we exclude the Moss- 
which have hitherto been generally 
polyps, and Tunicates 
classed with the tribe of Molluses—we retain as genuine 
Molluses the following four classes: Lamp-shells, Mussels, 
Snails, and Cuttles. The two lower classes of Molluses, the 
Lamp-shells and Mussels, possess neither head nor teeth, 
and they can therefore be comprised under one main class, 
or branch, as headless animals (Acephala), or toothless animals 
(Anodontoda). This branch is also frequently called that 
of the clam-shells (Conchifera, or Bivalvia), because all its 
members possess a two-valved calcareous shell. In contrast 
to these the two higher classes of Molluscs, the snails and 
cuttles, may be represented as a second branch with the name 
of Head-bearers (Cephalophora), or Tooth-bearers (Odonto- 
phora), because both head and teeth are developed in them. 
The soft, sack-shaped body in most Molluses is protected 
by a calcareous shell or house, which in the Acephala (lamp- 
shells and mussels) consists of two valves, but in the 
Cephalophora (snails and cuttles) is generally a spiral tube 
(the so-called snail’s house). Although these hard skeletons 
are found in large quantities in a petrified state in all the 
neptunie strata, yet they tell us but little of the historical 
development of the tribe, which must have taken place 
for the most part in the primordial period. Even in 
the Silurian strata we find fossil remains of all the four 
classes of Molluscs, one beside the other, and this, con- 
jointly with much other evidence, distinctly prove, 
that the tribe of Molluscs had then obtained a strong 
development, when the higher tribes, especially the 
