GET 



[ 332 J 



OSS 



Gr.) An extinct genus of poly- 

 thalamous, or many chambered, 

 cephalapods, which inhabited 

 straight shells. The orthoceratite 

 resembles an ammonite unrolled, 

 having its chambers separated by 

 transverse septa, concave externally, 

 and convex internally ; the septa 

 being pierced by a siphuncle. 

 Orthoceratites are abundantly found 

 in the transition strata, appearing 

 to have been early called into 

 existence, and at an early period to 

 have been consigned to almost total 

 destruction. At the close of the 

 Triassic period the Orthoceras ap- 

 pears to have become extinct. It 

 is regarded as characteristic of the 

 Palceozoic strata. Part of the 

 pavement of the palace at Hampton 

 Court, and that of the hall of Uni- 

 versity College, Oxford, are com- 

 posed of marble containing remains 

 of orthoceratites. Some species, 

 found in the carboniferous limestone 

 of Closeburn, in Dumfries-shire, 

 are nearly the size of a man's 

 thigh. 



OBTHOCOS'L A. A group of animalcules, 

 thus named from the straight 

 course of the intestine. 



O'BTHOCLASE. Called also potash- 

 feldspar; a mineral consisting of 

 silica 65*35, alumina 18'06, pot- 

 ash 16-59. 



OETHO'PTEEA. (from opOos, straight, 

 and Tnepov, a wing, Gr.) An order 

 of insects, the sixth in Cuvier's 

 arrangement. The coverings of the 

 wings, instead of being of a horny 

 texture, are soft and flexible. The 

 wings themselves, being broader 

 than their coverings, are, when not 

 in use, folded longitudinally like a 

 fan. 



O'ETHOSE. The name of a feldspathic 

 mineral. 



OEYCTOLO'GICAL, (from opvieros, a 

 fossil, and XoVyos, discourse, Gr.) 

 Pertaining to that part of physics 

 which treats of fossils. 



OEYCTO'LOGIST. One who studies, or 



is versed in, that part of physics 

 which treats of fossils. 



OEYCTO'LOGY. (from opvicros, a fossil, 

 and Xo<yos, discourse, Gr.) Oryc- 

 tology is that branch of mineralogy 

 which has for its object the classifi- 

 cation of fossils ; or, in other words, 

 it consists in the description of 

 fossils, the determination of their 

 nomenclature, and the systematic 

 arrangement of their different 

 species. Oryctology has also been 

 defined as the science which en- 

 quires into the nature, origin, and 

 formation of those bodies which 

 possess the figures, markings, or 

 structure of vegetables, or animals, 

 whilst their substance evinces their 

 having been preserved through 

 many ages, by certain changes 

 effected in subaqueous or subterra- 

 nean situations. 



OSCILLATION, (oscillatio, Lat. oscilla- 

 tion, Fr. oscillazione, It.) Vibra- 

 tion ; the act of swinging to and 

 fro ; a movement to and fro, like 

 the swinging of the pendulum of a 

 clock, or waves in water. The 

 tides are oscillations of the sea. 



OSMEEO'IDES MANTE'LLII. The name 

 given by Dr. Mantell to an ichthy- 

 olite of the chalk formation discov- 

 ered in the Lewes chalk-pits. It 

 is closely related to the smelt. 



O'SMITTM. (from oefir), odour, Gr.) 

 A metal discovered by Tennant in 

 crude platinum, and deriving its 

 name from the strong odour emitted 

 by some of its compounds. Its 

 symbols are 0. S. ; specific gravity 

 10-00. 



O'SSEOTJS BEE'CCIA. A mass of frag- 

 ments of the bones of animals, ce- 

 mented together by a calcareous 

 gangue, and commonly found in 

 fissures and caves. 



O'SSICLE. (pssiculum, a little bone, 

 Lat.) A small bone. 



OSSI'FEEOUS. (from os, a bone, and 

 feroy to produce, to bear, or contain, 

 Lat.) Yielding bones or fragments 

 of bones ; containing bones. Thus 



