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GLOSSARY. 
Opamzed Wood. Wood petrified by siliceous earth, and acquiring 
a structure similar to the simple mineral called opal. 
Ophidious Reptiles. Verteb rated animals, such as snakes and ser- 
pents. Etym., cxpig, opkis, a serpent. 
Organic Remains. The remains of animals and plants ; organized 
bodies, found in a fossil state. 
Orthocerata. An extinct genus of the order of Molluscous Ani- 
mals, called Cephalopoda, that inhabited a long chambered, 
conical shell, like a straight horn. Etym., opQog, orthos, straight, 
and tcepag, ceras, horn. 
Osseous Breccia. The cemented mass of fragments of bones of 
extinct animals found in caverns and fissures. Osseics is a Latin 
adjective, signifying bony. 
Outliers. When a portion of a stratum occurs at some distance, 
detached from the general mass of the formation to which it 
belongs, some practical mineral surveyors call it an outlier, 
and the term is adopted in geological language. 
Ovate. The shape of an egg. Etym., ovum, egg. 
Ovipositing. The laying of eggs. 
Oxygen. One of the constituent parts of the air of the atmosphere ; 
that part which supports life. For a further explanation of the 
word, consult elementary works on chemistry. 
Oxide. The combination of a metal with oxygen ; rust is oxide of 
iron. 
Pachydermata. An order of quadrupeds, including the elephant, 
rhinoceros, horse, pig, &c, distinguished by having thick 
skins. Etym. ira^vg, pachus, thick, and depjua, derma, skin or 
hide. 
Pachydermatous. Belonging to pachydermata. 
Paljsotherium, Paleothere. A fossil extinct quadruped, belonging 
to the order pachydermata, resembling a pig or tapir, but of 
great size. Etym. iraXaiog, palaios, ancient, and dtjpiov, therion', 
wild beast. 
Pelagian, Pelagic. Belonging to the deep sea. Etym. pelagus, 
sea. 
Peperino. An Italian name for a particular kind of volcanic rock, 
formed, like tuff, by the cementing together of volcanic «and, 
cinders, or scorise, &c. 
Petroleum. A liquid mineral pitch, so called because it is seen 
to ooze like oil out of the rock. Etym. petra, rock, and oleum, 
oil. 
Phane rogawic Plants, A name given by Linnaeus to those plants 
