PROOFS OF DESIGN IN AMMONITES. S55 
C07icl 
US 1071, 
On examining the proofs of Contrivance and 
Design that pervade the testaceous remains of 
the family of Ammonites, we find, in every spe- 
cies, abundant evidence of minute and pecuHar 
mechanisms, adapting the shell to the double 
purpose of acting as a float, and of forming a 
protection to the body of its inhabitant. 
As the animal increased in bulk, and advanced 
along the outer chamber of the shell, the spaces 
left behind it were successively converted into air 
chambers, simultaneously increasing the power 
of the float. This float, being regulated by a 
pipe, passing through the whole series of the 
chambers, formed an hydraulic instrument of 
extraordinary delicacy, by which the animal 
and rounded upwards towards the body of the ammal, (PI. 38, 
S. S.), and thus the jagged terminations of these lobes may have 
afforded holdfasts whereby the base of the mantle could fix itself 
firmly, and as it were take root, around the bottom of the exter- 
nal chamber. 
No such dentations exist in any species of Nautilus. In the 
N. Pompilius, Mr. Owen has shewn that the base of the mantle 
adheres to the outer shell, near its junction with the transverse 
plate by means of a strong horny girdle ; a similar contrivance 
probably existed also in all the fossil species of Nautili. The 
sides of the mantle also of the N. Pompilius are fixed to the 
sides of the great external chamber by two strong broad lateral 
muscles, the impressions of which are visible in most specimens 
of this shell. 
