a. [f. as prec. + -OUS.]

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  1.  = prec.

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1828.  in Webster.

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1851.  Mantell, Petrifact., i. § 3. 65. The foot-tracks are, for the most part, tridactylous (three-toed).

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1856–8.  W. Clark, Van der Hoeven’s Zool., II. 379. Feet tridactylous, palmate, with hallux none.

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  † 2.  Chem. Applied to a compound of an atom of one element with 3 atoms of another, as SO3. Obs.

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1865.  Mansfield, Salts, 483. The simple molecule Sn. … does not imitate the molecule Sb. in forming tridactylous compounds either with O. or with H.

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