A M M 



r 20] 



lions, lobated through their centre, 

 and pierced by a marginal tube. 



The ammonite differs greatly 

 from the chambered nautilus, the 

 whorls, or turns, being all distinct, 

 and in the same plane, and the 

 cells very small. The family of 

 ammonites extends through the 

 entire series of the fossiliferous 

 formations, from the transition 

 strata to the chalk inclusive. M. 

 Brochant, in his translation of De 

 la Beche's Manual of Geology, enu- 

 merates 270 species; these species 

 differ according to the age of the 

 strata in which they are found, and 

 vary in size from a line to more 

 than four feet in diameter. The 

 geographical distribution of am- 

 monites in the ancient world, seems 

 to have partaken of that univers- 

 ality we find so common in the 

 animals and vegetables of a former 

 condition of our globe, and which 

 differs so remarkably from the 

 varied distribution that prevails 

 among existing forms of organic 

 life. We find the same genera, 

 and, in a few cases, the same 

 species of ammonites, in strata 

 apparently of the same age, not 

 only throughout Europe, but also 

 in distant regions of Asia, and of 

 North and South America. Dr. 

 Gerard has found at the elevation 

 of 16,000 feet in the Himalaya 

 Mountains, species of ammonites, 

 identical with those of the lias at 

 "Whitby and Lyme Eegis. The 

 ammonite, like the nautilus, is 

 composed of three essential parts : 

 1st. An external shell, usually 

 of a flat discoidal form, and having 

 its surface strengthened and orna- 

 mented with ribs. 2nd. A series 

 of internal air chambers, formed by 

 transverse plates, intersecting the 

 inner portion of the shell. 3rd. A 

 siphuncle, or pipe, commencing at 

 the bottom of the outer chamber, 

 and thence passing through the 

 entire series of air chambers to the 



AMP 



innermost extremity of the shell. 

 The most decided distinction be- 

 tween ammonites and nautili is 

 founded on the situation of the 

 siphon. In the ammonite, this 

 organ is always on the back of the 

 shell, but never so in the nautilus. 



The opinions of geologists and 

 conchologists have greatly varied 

 as to the situation and use of the 

 shell of the ammonite ; Cuvier, 

 Lamarck, Bakewell, and others, 

 have supposed that the shell was 

 an internal one ; but the reasoning 

 of Buckland on this subject seems 

 conclusively and indisputably to 

 prove that the shell was external. 



ADIMONITI'FEROTJS. Containing the 

 remains of ammonites. 



AMMONO'CEEAS. | (from ammon, 



AMMONOCE'EATITES. j and /ce/?as-, Gr.) 

 The shells of this genus resemble 

 ammonites in their internal struc- 

 ture, but that they are only curved 

 instead of being spirally convolute. 



A'MPELITE. (from o/wreXos, Gr. a 

 vine.) A kind of aluminous slate, 

 belonging to both the fossiliferous 

 and metamorphic series of rocks. 



AMJPHI'BIA. (from a^l and /3/os, Gr.) 

 A class of animals possessing the 

 property of living either in the 

 water or on dry land ; undergoing 

 a metamorphosis whereby the gills 

 become obliterated and the lungs 

 developed, while the heart, from 

 being bilocular, or possessing two 

 cavities only, obtains three cavi- 

 ties, namely, two auricles and one 

 ventricle. 



The fourth class of the sub- 

 kingdom Vertebrata, kingdom Ani- 

 malia. In this class are com- 

 prised four orders, namely, Laby- 

 rinthodonta, Batrachia, Sauroba- 

 trachia, and Ophiomorpha. The 

 lungs of the amphibia differ greatly 

 from those of animals of the classes 

 aves and mammalia. Their body 

 is covered with a shell, or with 

 scales, or is quite naked. They have 



