AMMONITES. 



61 



Fig. 62. Ammonites nodosvs. 



The Ammonites, (Jig. 62), or Co'rnua Ammonis so called from a sup 

 posed resemblance to the horns engraven on the heads of Jupiter Ammon 

 are among the most common and well-known fossils. Local legends, 

 ascribing their origin to swarms 

 of snakes turned into stone by 

 the prayers of some patron saint, 

 are still extant in certain parts 

 of England, and perpetuated by 

 the name of snake-stones, by 

 which these fossils are provin- 

 cially known. Several hundred 

 species have been described ; 

 they are divided into genera, 

 which are characterized by es- 

 sential modifications in the di- 

 rection of the spire, and the 

 inflections of the septa. 



The shell of the ammonite is 

 generally thinner and more deli- 

 cate than that of the nautilus, (to which it bears considerable resemblance), 

 and in some species it resembles the flexible covering of the argonaut; pos- 

 sibly, in these species the animal, like the recent paper nautilus, may have 

 possessed a pair of arms terminating in broad membranous expansions, 

 which secreted the shell, and generally remained in contact with it; other- 

 wise it is difficult to explain how such delicate fabrics should have been 

 uninjured. 



The living and extinct species of testaceous cephalopods, " are all con- 

 nected by one plan of organization ; each forming a link in the common 

 chain which unites the existing species with those that prevailed among the 

 earliest conditions of life upon our globe, and all attesting the identity of 

 the design that has effected so many similar ends, through such a variety 

 of instruments, the principle of whose construction is, in every species, fun- 

 damentally the same. 



" Throughout the various living and extinct genera of these beings, the 

 use of the air-chambers and siphon of their shells, to adjust the specific 

 gravity of the animals in rising and sinking, appears to have been identical. 

 The addition of a new transverse plate within the coiled shell added a new 

 air-chamber, larger than the preceding one, to counterbalance the increase 

 of weight that attended the growth of the shell and body of these ani- 

 mals." Buckland. 



The occurrence of the nautilus and its congeners among the earliest 

 traces of the animal kingdom, and their continuance throughout the im 

 mense periods during which the family of ammonites was created, flour- 

 ished, and became extinct, and the existence of species of the same genus 

 at the present time, are facts too remarkable to have escaped notice. To 

 these facts Mrs. Howitt alludes in the following lines to the nautilus : 



"Thou didst laugb at sun and breeze 



In the new created seas ; 

 Thou wast with the reptile broods 

 In the old sea solitudes. 

 Sailing in the new-made light, 

 With the curled-up ammonite. 

 Thou surviv'dst the awful shock, 

 Which tiirn'd the ocean-bed to rock, 

 And changed its myriad living swarnut 

 To the marble's veined forms." 



See Manteirs Medals of Creation. 



