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N A U 



Mbnodon monoceros of Linnaeus. 

 Placed by Cuvier in the family 

 Cetacea ordinaria, order Cetacea. 

 The tusk of this animal is some- 

 times ten feet long, and spirally 

 furrowed. Portions of the skull of 

 the narwahl have been found in 

 the Lewes levels, in Sussex. 

 NA'SSA. A genus of fossil univalve 

 shells separated from Buccinum by 

 the tooth-like projection which 

 terminates the columella ; ten fossil 

 species are recorded in the English 

 tertiary deposites, and two from the 

 green sand of Black Down, but the 

 genus of the latter is perhaps rather 

 doubtful. 



NA'TATOEY, (from natator, Lat. a 

 swimmer.) Enabling to swim. 

 Certain organs possessed by many 

 animals are natatory organs. Seve- 

 ral of the cephalophods and ptero- 

 pods, and other molluscans, have 

 natatory appendages. 

 NA'TICA. A genus of nearly globose, 

 umbilicated, univalves, belonging 

 to the family Neritaeea. Aperture 

 entire and semicircular ; columella 

 transverse, without teeth, and 

 callous externally. These shells, 

 though strongly resembling Neri- 

 tse, may be distinguished from 

 those of that genus by their being 

 always umbilicated, and the colu- 

 mella never dentated. The recent 

 Natica is found in estuaries and 

 tidal rivers, in mud and sandy mud, 

 at depths varying to forty fathoms. 

 It is also found fossil. 

 NA'TEOLITE. The Natrolith of Wer- 

 ner; Natrolithe of Hau'y; con- 

 sidered by some mineralogists to be 

 a variety of prismatic zeolite. 

 Occurs in small, reniform, rounded, 

 or irregular masses, composed oi 

 very minute fibres ; the fibres are 

 divergent, or even radiate from a 

 centre, and are sometimes extreme- 

 ly minute and close. Colours 

 yellow, yellowish brown, and 

 brown, with striped-colour deline- 

 ations. Translucent at the edges 



Sp. gr. 2*16, to 2-20. Before the 

 blow-pipe it fuses readily into a 

 white glass. In nitric acid it is 

 reduced, without any effervescence, 

 into a thick jelly. It derives its 

 name from containing soda. Its 

 constituents are silex 48 '20, alu- 

 mine 24-50, soda 16-10, oxide of 

 iron 1*75, water 9'0. It occurs 

 principally at Roegau, in Suabia, 

 imbedded in amygdaloid. 

 NA'TRON. (natron, Fr.) The Soude 

 carbonatee of Haiiy ; L'alkali min- 

 eral natif of Brochant ; the Natron 

 of Kir wan. A carbonate of soda 

 occurring massive and crystallised, 

 the principal supplies coming from 

 lakes in Egypt and Hungary. In 

 Egypt, the lakes which yield 

 natron abundantly are called the 

 Lakes of Natron. These are six in 

 number, to the westward of the 

 Nile, not far from Terrana, in a 

 valley, surrounded by limestone. 

 NA'TUEAL HISTOEY. This extensive 

 science has for its object the 

 enquiry into the being of natural 

 bodies, and their thorough investi- 

 gation in reference to their various 

 qualities, and the relative functions 

 of their component parts. Under- 

 stood in this extent, it presents us 

 with a distinct unique entirety, 

 which treats the natural body as 

 complete, but gradually perfected ; 

 and at the same time seeks to dis- 

 cover the means whereby it at- 

 tained its completion and perfection. 

 Natural history, therefore, is no 

 mere description of form, no 

 description of nature, as it has been, 

 latterly, very incorrectly considered, 

 but a true and pragmatical history, 

 developed from its own funda- 

 mental principles. Burmeister. 

 NAU'LAS. A genus of ichthyolites of 



the old red sandstone. 

 NATJTILA'CEA. A family of Polytha- 

 lamous cephalopods, in the arrange- 

 ment of Lamarck. This family 

 comprises Discorbites, Nautilus, 



