268 PROOFS OF DESIGN IN AMMONITES. 



The uses ascribed by Von Buch to the lobes of Am- 

 monites in affording attachment to the base of the mantle 

 around the margin of the transverse plates, would in no 

 way interfere with the service we have assigned to the same 

 lobes, in supporting the external shell against the pressure 

 of deep water. The union of two beneficial results from 

 one and the same mechanical expedient, confirms our opi- 

 nion of the excellence of the workmanship, and increase our 

 admiration of the Wisdom in which it was contrived. 



Conclusion. 



On examining the proofs of Contrivance and Design that 

 pervade the testaceous remains of the family of Ammonites, 

 we find, in every species, abundant evidence of minute and 

 peculiar mechanisms, adapting the shell to the double pur- 

 pose of acting as a float, and of forming a protection to the 

 body of the inhabitant. 



All the lobes, as they dip inward, are subdivided by numerous dentations, 

 which afford points of attachment to the mantle of the animal; thus each 

 lobe is flanked by a series of accessory lobes, and these again arc provided 

 with farther symmetrical dentations, the extremities of which produce all 

 the beautiful appearances of complicated foliage, which prevail through the 

 family of Ammonites, and of which we have a striking example on the sur- 

 face of PI. 38. 



The extremities of the dentations are always sharp and pointed, inwards, 

 towards the air-chamber, (PI. 38, d. 1.;) but are smooth and rounded up- 

 wards towards the body of the animal, (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 external chamber. 



No such dentations exist in any species of Nautilus. In tlic N. Pompi- 

 lius, Mr. Owen has shown 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. 



