C T 



[ 322 



OLD 



kcuhis t a cell or pocket, Lat.) Eight- 

 celled. 



OCTONO'CULAB. (from octo, eight, and 

 oculus, an eye, Lat.) Having eight 

 eyes. 



OCTOPE'TALOUS. (from OKTW, eight, 

 and TreTrtXoi/, a petal, Gr.) Having 

 eight petals or flower-leaves. 

 OCTOSPE'BMOFS. (from OKT-W, eight, 

 and aTrep/Lui, seed, Gr.) Eight- 

 , seeded ; having eight seeds. 

 ODONTACA'NTHUS. A genus of ichthy- 

 olites of the old red sandstone for- 

 mation, previously known as C ten- 

 op tychius, but for which Odonta- 

 canthus has been substituted. Two 

 species have been described by 

 Agassiz. 



(Eso'pHAGUS. (cesophage, Fr.) The 

 gullet, or passage leading from the 

 mouth to the stomach, through 

 which the food passes. In the 

 structure of the oesophagus, we 

 may trace an adaptation to the 

 particular kind of food taken in by 

 the animal. When it is swallowed 

 entire, or but little changed, the 

 oesophagus is a very wide canal, 

 capable of being greatly dilated. 

 Serpents, which swallow animals 

 of greater circumference than them- 

 selves, have an oesophagus admit- 

 ting of great dilatation ; the food 

 in such cases remaining a long time 

 in the canal, before it reaches the 

 stomach. Grazing animals, who 

 carry their heads close to the ground 

 while feeding, have the oesophagus 

 strengthened by thick muscular 

 coats, whereby the food is propelled 

 towards the stomach, the direction 

 being contrary to that of gravity. 

 OGY'GIA. The name given by Brong- 

 niart to a genus of trilobites; he 

 thus defines the generic characters : 

 "Corps tres deprime*, en ellipse 

 allonge*e, non contractile en sphere. 

 Bouclier horde* ; un sillon peu pro- 

 fond, longitudinal, partant de son 

 extre'mite' ante*rieure. Pointd'autres 

 tubercules que les oculiformes. 

 Lobes longitudinaux peu saillans. 



Huit articulations a 1'abdomen." 

 In establishing this genus, M. 

 Brongniart observes that although 

 its appearance is very different 

 from that of most other genera of 

 the family of trilobites, yet it is 

 not always easily separated from 

 them. 



OGY'GES. The name given by Guet- 

 tard to a species of trilobite, from 

 its being found among the most 

 ancient rock formations, containing 

 vestiges of organic life. 

 O'KENITE. A bi-silicate of lime, with 



two equivalents of water. 

 OLD EED SANDSTONE. (The Gres rouge 

 intermediare of the French; the 

 Jiingeres Grauwackengebirge, and 

 Alter rother sandstein of the Ger- 

 man geologists.) The lowest mem- 

 ber of the carboniferous group, 

 extensively developed in the coun- 

 ties of Shropshire and Hereford- 

 shire, in England ; Brecknockshire, 

 in Wales; and Dumfriesshire and 

 Forfarshire, in Scotland. The old 

 red sandstone strata lie between 

 the carboniferous series and the 

 silurian rocks, or grauwacke group. 

 It consists of many varieties and 

 alternations of silicious sandstones 

 and conglomerates of various colors, 

 red predominating. The old red 

 sandstone of some countries gradu- 

 ates into grauwacke, and it is the 

 opinion of most continental geolo- 

 gists that it should be considered as 

 forming the upper portion of the 

 grauwacke series. The old red 

 sandstone is a course-grained, mi- 

 caceous sandstone, evidently of 

 mechanical origin, constituted ap- 

 parently of abraded quartz, felspar 

 and mica, and containing fragments 

 of quartz, clay-slate, flinty-slate, 

 &c. ; sometimes passing into the 

 state of a quartzose conglomerate, 

 sometimes possessing a structure 

 coarsely schistose, and sometimes, 

 particularly towards its lower re- 

 gions, becoming finely schistose, 

 and passing into a fine-grained 



