160 

 Genus 3. NERITA, Linnceus. 



Animal ; very similar to that of Neritina, the disk being rather 

 stouter. 



Shell ; semiglobose, solid, smooth, sometimes ribbed, spire small and 

 indistinct, columella transversely flattened, sometimes crenulated 

 or toothed, aperture semicircular, frequently grooved within, 



The animal of Nerita differs so little from Neritina, that naturalists have 

 been somewhat divided as to the propriety of separating these genera. The 

 genus Cerit/dum presents an instance in which the changes are considerable 

 in the composition and substance of the shell, arising out of differences of 

 habit, some being marine, others dwelling in estuaries and situations where 

 the water is only brackish, and others again living in the vicinity of springs 

 or stagnant marshes, quite beyond the influence of the tide. So it is with 

 the Nerita and Neritina, and were it not that collectors are in the habit of 

 distinguishing them, agreeably with the views of Lamarck, since whose time 

 no new facts have been elicited in their natural history, they would have 

 been here fused into one. 



The Sea-Nerites construct shells of very solid growth, and paint them 

 with extremely vivid colours ; the colours are, moreover, so variable in the 

 same species that it is only by a close observation of form and general 

 design, that their specific relation is understood. With this robust struc- 

 ture and display of colour, the shells of this genus are also characterized by 

 variations of sculpture which are not found in the fresh-water genus. 

 Many of the species are strongly ribbed, the interior of the shell being 

 marked with corresponding grooves, and the edge of the lip more or less 

 strongly crenulated, others have the flat columellar septum granulated, and 

 in some species, such as in that selected for illustration, N. ornata, and the 

 well-known Bleeding-tooth, Npeloronta, it is dentated. 



The Nerita, like the Neritina, are very generally distributed throughout 

 the globe ; but are rather more confined to the equatorial regions. Few 

 species, if any, remain undescribed ; the entire family of the Neritacea has 

 been investigated with minute accuracy by M. Recluz of Paris, to whom 

 Mr. Cuming, with a proper international spirit, forwarded the new species 

 resulting from his researches in the Philippine Islands. 



Species. 



1. Adansonia, Recluz. 4>. Antillarum, Gmelin. 7. argus, Recluz. 



2. albicella, Linn. 5. antiquata, Recluz. 8. atrata, Chemn. 



3. Anatolica, Recluz. 6. apiata, id. 9. atropurpurea, Recluz. 



