446 



{Errntfurn of Datura! 



inside smooth ; operculum shelly in some 

 specks, horny in others ; epidermis thin, 

 light, and transparent. The he:id of the 



animal is very large, having two tentacula 

 with eyes at the base ; foot large and thin. 

 The straight, callous, smooth edge of the 

 columella serves to distinguish this genus 

 from Nerita, Helix, &c. There are very 

 many recent marine species, and not a few 

 fossil. 



NATRIX. A genus of Colubridce, a family 

 of snakes destitute of poison-fangs ; of which 

 our common harmless snake (Coluber natrix") 

 is a type. [See SXAKE.] 



NATTER-JACK. (Bufocalamita.) The 

 English name of a species of Toad, of a 

 lightish yellow colour, inclining to brown, 

 and clouded with dull olive ; but its most 

 distinguishing mark is a bright yellow line 

 running down the middle of the back. It 

 never leaps, nor does it crawl with the slow 

 pace of a toad, but its motion is more like 

 running. They are found in considerable 

 numbers near stagnant pools and ditches, 

 where they congregate for the purpose of 

 breeding ; and their hoarse voices are heard 

 at a great distance. 



NAULTINUS. A genus of Lizards, con- 

 taining four or more generally green coloured 

 species, natives of New Zealand. They are 

 allied to the Geckos. 



NAUTILITES. The name given to nu- 

 merous chambered shells existing in a fossil 

 state, nearly resembling the Nautilus, above 

 described, and which are found in almost 

 all marine strata, from the oldest limestones 

 and sandstones of the Silurian system, down 

 to those overlying the chalk. 



NAUTILUS. (Nautilus Pompilius.-) The 

 Pearl Nautilus, so named from the nacreous 

 lining of its shell, belongs to a genus of 2'e- 

 truln-anchiate Cephatopods; but though the 

 shell of this animal is well known, being 

 found in the seas of most tropical latitudes, 

 the most vaaue and incorrect ideas were, 

 until lately, formed of its living inhabitant : 



we believe, indeed, it was only in 1820 that 

 this animal was known v.'iih any certainty, 

 one having been caught alive by Mr. G. 



Bennett, near the New Hebrides Islands ; 

 which, preserved in spirits, is now in the 

 museum of the College of Surgeons. The 

 Nautilus is very rarely met with in the 

 living state, owing to its being an inhabitant 

 of the open sea, and possessing the power of 

 sinking at the slightest alarm. Externally 

 the shell presents nothing remarkable, being 

 a flattened spiral ; but on examining its 

 interior, we find it divided into chambers, 

 by a large number of transverse partitions 

 of shelly matter ; sometimes as many as 

 thirty or forty separate chambers or divi- 

 sions, each communicating with the rest by 

 a small tubular hole near the centre. The 

 opening or mouth of the shell therefore 

 presents a large but shallow concavity, 

 pierced with a central or nearly central hole ; 

 while beyond it lie all the divisions adverted 

 to. The outer chamber is by far the largest, 

 and to this the body of the animal is re- 

 stricted ; but it maintains a connection with 

 the rest by means of a membranous tube, 

 called the siphuncle, which passes through 

 the centre of each partition, and thus pene- 

 trates even to the innermost and smallest 

 chamber. These animals are furnished with 

 numerous tentacula, short, slender, and un- 

 provided with suckers. They usually re- 

 main at the bottom of the water, and are 

 able to creep along rather quickjy, support- 

 ing themselves upon their tentacula, with 

 the head downwards, and the shell raised 

 above. After stormy weather, as it becomes 

 more calm, they may be seen, in great 

 numbers, floating upon the surface of the 

 waves, with the head put out, and the ten- 

 tacula resting upon the water, the shell at 

 the same time being undermost : they re- 

 main, however, but a short time sailing in 

 this manner, as they have the power of easily 

 returning to their situation at the bottom of 

 the sea, by merely drawing in their ten- 

 tacula and upsetting the shell. 



NAVICELLA. A genus of fluviatile 

 Mollusca, inhabiting the clear rivers of India, 

 the Isle of France, &c. The shell is trans- 

 versely oval ; dorsal surface convex ; with 

 the apex straight and bent down to the edge, 

 not spiral ; operculum testaceous, flat, sub- 

 quadrate, with a lateral articulation ; the 

 shell, indeed, altogether much resembling a 

 Patella. The animal is distinguished by a 

 large head, having two tentacula, the eyes 

 placed on the summit of two small protube- 

 rances at their base ; foot large : they creep 

 well on the rocks, and do not continue fixed 

 to one spot. 



NAXIA. A genus of short-tailed De- 

 capod Crustacea, containing some singular 

 spine-fronted species of Crabs, found in the 

 Eastern Seas. 



NEBALTA. A genus of singular Crus- 

 tacea belonging to the Entomostraca, order 

 Phyflopoda, and containing two or more in- 

 tcres';ng British species. 



NECROPIIAGA. The appellation given 

 by Latreille to an extensive group of Cole- 

 opterous insects, highly serviceable in re- 

 moving the decaying remains of animal 

 matter and such kinds of impurities. Ac- 



