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nal of Arts and Sciences : they 

 were discovered in the new red 

 sandstone of the valley of Connecti- 

 cut. The most remarkable were 

 those of a gigantic bird, twice the 

 size of an ostrich, whose foot mea- 

 sured fifteen inches in length, ex- 

 clusive of the largest claw, which 

 measured two inches. The dis- 

 covery of these ornithicknites is 

 exceedingly interesting to the pal- 

 aeontologist, as proving the exist- 

 ence of birds at the early epoch of 

 the new red sandstone formation. 



OBNI'THOLITE. (from opvn, a bird, 

 and \j0os, a stone, Gr.) A fossil 

 bird. Stones of various colours 

 and forms, bearing the figures of 

 birds. Specimens of this kind may 

 be obtained at Matlock, in Derby- 

 shire, and at other places where the 

 water is surcharged with lime. 

 The gypsum quarries of Paris con- 

 tain the debris of birds in great 

 abundance. The feet are the most 

 remarkable part in all the ornitho- 

 lites, the feet of birds being com- 

 posed in a peculiar way, not 

 resembling those of any other 

 animals. 



OBNITHO'LOGY. (from opvis, a bird, 

 and XJcyos, discourse, Gr.) That 

 department of natural history which 

 treats of birds; describes their 

 structure, external and internal ; 

 and teaches their economy and 

 their uses. 



OBNITHO'LOGIST. One versed in that 

 branch of natural history which 

 treats of the habits, structure and 

 uses of birds. 



OBNITHORHY'NCHUS. (from opvi?, a 



- bird, and pvy-xps, a beak, Gr.) 

 The platypus of Shaw. The duck- 

 bill ; an animal indigenous to New 

 Holland, and found in no other 

 country. In this anomalous ani- 

 mal, we have a quadruped clothed 

 with fur, having a bill like a duck, 

 with four webbed feet, suckling its 

 young, and most probably ovo- 

 viviparous : the male is furnished 



with spurs. The mouth of the 

 ornithorhynchus has a form of con- 

 struction between that of quadru- 

 peds and birds, being furnished, 

 like the former, with grinding teeth 

 at the posterior part of both the 

 upper and lower jaws, but they are 

 of a horny substance; the mouth 

 is terminated in front by a horny 

 bill, greatly resembling that of the 

 duck, or the spoon-bill. It has 

 also small cheek-pouches. Mem- 

 branes unite the toes of the fore 

 and hind- feet; in the fore-feet it 

 extends beyond the nails, in the 

 hind-feet it terminates at the root 

 of the nails. It has also a flattened 

 tail. It inhabits the rivers and 

 marshes. 



O'RPIMENT. (from auripigmentum, Lat. 

 orpiment, Pr. orpimento, It.) The 

 Arsenic sulfure jaune of Hauy; 

 Arsenic sulfur^ orpiment of Brong- 

 niart. Yellow sulphuret of arsenic, 

 an ore of arsenic combined with 

 sulphur. Its colour is usually 

 lemon-yellow, which is often shin- 

 ing and beautiful. It occurs in 

 laminated or lamellar masses ; in 

 concretions; and sometimes in 

 minute crystals. It is principally 

 volatilized before the . blow -pipe, 

 with a white smoke, and with the 

 odour of both sulphur and arsenic, 

 leaving a small earthy residue. 

 According to Thenard it is composed 

 of arsenic 57, sulphur 43. 



O'BTHIS. (from opQos, straight, Gr.) 

 A genus of fossil shells, constituting 

 a division of spirifer, but distin- 

 guished from spirifer by the long 

 narrow hinge and circular flat form 

 of the striated shells. Twenty-six 

 species of the genus orthis are 

 enumerated by Sir R. Murchison 

 as occurring in the Silurian rocks. 



O'BTHITE. A mineral found in the 

 mine of Finbo, in Sweden, and 

 thus named from its being always 

 found in straight layers. 



OBTHO'CERAS. } (opOos, straight, 



OBTHOCE'BATITE. ) and */>?, a horn, 



