MINERALOGY. 



457 



Oryctogno* A. Petrifactions from the Animal Kingdom. 



y- a. Quadrupeds. The fossil remains of quadrupeds 



>< "Y"' are generally found but little altered, and in single 

 pieces, as bones, teeth, and horns ; seldom in com- 

 plete skeletons. The greater number of species 

 found in this state appear to be extinct . 



b. Birdt. The remains of birds, which are usually 

 single bones, feet, claws, and bills, are very rare ; 

 they have been found in the vicinity of Mont 

 Martre, near Paris, and in the limestone of JEaia- 

 gen and Pappenheim. 



c. Amphibious Animals. Fossil remains of tortoise* 

 and crocodiles have been met with in different 

 parts of Europe. Fossil tortoises occur in the Isle 

 of Shepey in the Medway ; and fossil remains of 

 animals allied to the crocodile, are met with in 

 the neighbourhood of Bath, in the cliffs on the 

 Dorsetshire coast, and also on the coast of York, 

 ihire. 



J. Fishes. Of these we find petrified, either the en- 

 tire fish, skeletons, vertebra?, or teeth. Of the 

 entire fish, instances have been observed in the 

 copper or marl slate of the county of Mansfeld ; 

 and also in Oxfordshire, Gloucestershire, Leices- 

 tershire, Lincolnshire, Dorsetshire and Kent t ; 

 of the skeletons in the limestone of Pappenheim ; 

 of the vertebrse in Shepey ; of the teeth, particu- 

 larly those of the (hark, considerable quantities in 

 the Island of Malta, and also in Kent and Isle of 

 Shepey. 



f. Insects. These are very rare. The only well au- 

 thenticated instances of petrified fresh water in- 

 sects, are the larvoe of libellula.*, found in the 

 limestone of Pappenheim. Of sea insects, a very 

 considerable variety have been discovered. Of 

 the genus cancer, several distinct species have 

 been found in the Isle of Shepey, in the Med- 

 way. 



Insects inclosed in amber are not to be regard- 

 ed as petrifactions, because they are dead bodies 

 nearly unaltered. 



f. .Sht-lls. Many genera of fossil shells are enumer- 

 ated by author*. It is sufficient for our present pur- 

 pose to remark, that these fossil remains are un- 

 commonly numerous, and are for the most part of 

 species which have never been found in a living 

 state. 



g. Crustaceans Animals. Of these, the most remark- 

 able and abundant are the Echinites and Aste- 

 rites. 



A. Carols. Many different fossil genera and species 

 of these bodies have been figured and described 

 by naturalists, under the names Madreporites, Mil* 

 leporites, Fungites, tec. 

 B. Petrifactions from the Vegetable Kingdom. 



These are, 



a. Impreuioiu of plants and leaves. These occur very 

 frequently, and appear to characterise particular 

 formations. Thus, the impressions and casts of 



reeds and ferns appear to occur most frequently Oryctogno- 

 in the bituminous shale and slate- clay of the coal ._/*_,_,, 

 formation. Petrifactions of seeds and fruits also 

 occur in sandstone and other rocks. 

 b. Transmuted n-ood, or petrified wood. It occurs in 

 the form of trunks, branches, or roots. The 

 wood is either petrified with an earthy mineral, 

 as in wood-stone and wood-opal ; with a metal- 

 liferous mineral, as in pyritical wood; or it is 

 bituminous, as in the different kinds of brown- 

 coal +. 



II. The External Surface. 



The external surface of minerals is either smooth, The Exter- 

 or more or less uneven. When the inequalities he- J~ e * ur ' 

 come so great as to affect the shape, they are no longer 

 considered as characterising a variety of surface, but 

 as a variety of external form. 



The following are the varieties of this character. 



1. Uneven. This, of all the kinds of external surface, 

 presents the greatest and most irregular elevations 

 and depressions, yet they are not so considerable as 

 to alter th external shape. Example, Surface of 

 balls of calcedony. 



2. Granulated. When the surface shews numerous 

 small nearly similar roundish elevations, that appear 

 like grains strewed over it, it is said to be granulat- 

 ed. It has a striking resemblance to shagreen. 



3. Rough. This kind of surface is marked with small 

 scarcely visible elevations, which we can hardly dis- 

 cover but by the feel. It has little or no lustre. Ex- 

 amples, Rolled pieces of common quartz and rock- 

 crystal. 



4. Smooth. Here there is no perceptible inequality, 

 and the surface reflects more light than the preced- 

 ing kinds of external surface. Examples, Flnor- 

 spar, cubes of galena or lead-glance. 



;.. '^treated. This kind of surface is marked with 

 line-like elevations. It is either limply streaked or 

 doubly streaked. 



A. Simply streaked, when the line-like elevations run 

 but in one direction. 



a. Longitudinally streaked. When the streaks are 

 parallel with the length of the lateral planes. Ex- 

 ample, Topaz. 



b. Transversely streaked. When the streaks are pa- 

 rallel with the breadth of the lateral planes. Ex- 

 ample, Hock-crystal. 



c. Diagonally streaked. Where the streaks are pa- 

 rallel with the diagonal of the planes. We have 

 an example of it in the garnet, where the streaks 

 pass through the obtuse angle of the rhomboid. 



d. Alernaiily streaked. When transverse and longi- 

 tudinal streaks occur on alternate planes. Exam- 

 ple, Cubic iron-pyrites. 



B. Doubly streaked, when the streaks run in different 

 directions. This is either 



a. Plumiformly. When the streaks run obliquely 



1 t may be remarked, that the foidl remains of the human ipeciei rarely *ccur ; the only well-authenticated example of thii kind 

 being the human skeleton imbedded in an alluv.il calcareous man brought from Guadaloupe by Sir Alexander Cochrane, and now pre- 

 eaud to the Brituh Museum by Lord Melville ; nor should the rarity of their occurrence excite our wonder, when it U recollected that 

 tutata bones an looter in thcu texture, and more cellular than thote of quadruped*, and therefore much more liable to decomposition. 



f ParkinMo'i OrMfc femm.*, voL iii- p. 49. 



t The best English week on Petrifaction*, is that of Mr. Parkinson, entitled, " Orpnlc Rcmaintffa Former World." It abound. 

 in eurioui and important information, and U adorned and mounted with numerous beautiful plate*. Mr. Sowerby u pubfohing a useful 

 oik, entitled, " Mimnl C<mc*<*fy." And the valuable observation, on Organic Benaina, in UM Transaction* of the Geological So- 



TOL. XIV. TART It. 



3 M 



