THE 



ENGLISH CYCLOPAEDIA. 



NATURAL HISTORY. 



NERITIDyE. 



NERITUXE. 



XERITIDJE, a family of Holostoruatous (iaiteropoda, having the 

 following characters: Shell thick, semiglobose ; spire very email; 

 cavity simple from the absorpition of the internal portion of the 

 whorla ; aperture semi-lunate ; columellar side expanded and flattened ; 

 outer lip acute; operculum shelly, sub-spiral, articulated. At the 

 end of the columella there is an oblong muscular impression, con- 

 nected ou the outer side by a ridge on which the operculum rests ; 

 within this ridge the inner layers of the shell are absorbed. Animal 

 with a broad short muzzle, and long slender tentacles; foot oblong, 

 triangular ; teeth 7, uncini very numerous. This family includes the 

 genera Nerita, Pileoltu, Neritina, and Navicella. 



Linnaeus placed the genus Ntrita between Helix and Haliotu, and 

 he divided the genus iuto the following sections : 



* Umbilicata. 



Species : N. canrena, N. ylaucina, N. vitcllut, N. albumen, N. matn- 

 rniUata. 



" Imperforate, with a toothless lip. 



Species : N. corona, If. radula, N. cornea, N. fluviatilii, N. litloralii, 

 and N. laciutrit. 



** Imperforate, with a toothed lip. 



Species : A'. )>ulligera, N. pupa, N. bideni, N. viridit, N. Yiryinea, 

 N. folita, N. peloronta, N. albicila, N. hittrio, N. plicata, N. groua, N. 

 Chtima-Jeon, N. undata, and N. cxuvia. 



We find then, that, in the ' Systema Naturae,' Linnaeus made no 

 marked distinction between the marine and freshwater Xerits. 



The Neritacea of Lamarck comprise the genera Navicella, Neritina 

 (Freshwater Nerits), Nerita (Marine Nerits), Natica and Janthina. 



Cuvier makes the Nerites (Nerita, Linn.) immediately follow 

 Janthina, and includes under them Nalica, Lam. ; the Nerita, pro- 

 perly so called (Nerita, Lam. ; Peloronta, Oken) ; Velatei, Montf. 

 i perverts, Omel., a large fossil species); Neritina, Lam. and 

 Clilkon, Montf. (the Crowned Neritines). 



M. De Blainville'a Jlemicydostomata, equivalent to Nerita, Linn., 

 comprise the 1 genera Natica, Nerita, and Navicella, or, as he terms it, 

 Seplaria. 



Nerita he divides iuto the following sections : 



* Right lip toothed. (Qenus Nerita, Lam.) 



A. Species with a single median toothed on the left lip. (Genus 

 Peloronta, Oken.) Ex. Nerita peloronta. 



B. Species with two teeth. Ex. N. exuvia. 



C. Species with three or four teeth. Ex. N. lineata. 



' The right lip not toothed. (Genus Neritina, Lam.) 

 1). Species less thick, with the right lip trenchant, and tlie oper- 

 culum very oblique. (Genus Neritina, Lam.) Ex. Neritina 

 Jturialilii. 



E. Species whose columellar lip Is toothed, and which are pro- 

 vided with spines. Ex. Nenla canora. 



F. Species with the columellar lip toothed ; the two extremities 

 of the right Itp prolonged much beyond the aperture, and 

 forming, with the callosity which covers the columellar lip, a 

 fort nf auricle produced by the tentacular lobe of the animal. 

 Kx. N. auriculata. 



JUT. BIST. D1V. VOL. IV. 



0. Calyptroid species, with the upper summit vertical and spired ; 

 the last whorl forming the whole base of the shell, and occupied 

 below by a large callosity, which sometimes covers the whole 

 spire. (Genus Yelatet, Montf.) Ex. N. perverta. 



If. Patelloid species, which are elongated, non-symmetrical, with a 

 dorsal summit, and not spired. (Genus Pileolia, Sow.) Ex. 

 N. altavillentii. 



M. De Blainville observes that this genus is formed of marine and 

 fluviatile species, which led Lamarck to subdivide it into two genera, 

 according to the thickness of the shell, which is greatest in the first, 

 and the denticles on the right lip, which arc entirely null iu the 

 second. M. De Blainville's observations lead him to the conclusion 

 that the species are still more easily distinguished by the sculpture 

 (guillochis) of the external surface of the operculum than by any other 

 character. He remarks that Lamarck enumerates 17 species of Marine 

 Nerits, which are all from the equatorial and southern seas, and 21 

 River Nerits, or Neritincf, two of which only are European, and the 

 others belonging to America and Asia. 



M. De Blainville states that only two fossil Nerits are known and 

 two Pileoli. But immediately afterwards he says that Defrauce 

 reckons five species of fossil Nerits, two of which are analogues (Italy) 

 according to Brocchi ; and five species of Neritina, two from the same 

 country, and four Pileoli. 



M. Rang adopts the arrangement of M. De Blainville, and condemns 

 Lamarck for generically separating the marine and freshwater Nerits. 

 M. Hang .-ays that there are many species of fossil Nerits. 



Mr. Swaiuson places the family Naticidce between his Turbidte and 

 Trochidcf, making it consist of the following sub-families and genera. 

 His arrangement is, he says, founded ou the shells only, from ignorance 

 of the ruimals of the major part : 



Sub-Family 1. Noticing. Sea-Snails. 



Genera: Natica, Lam. (with the sub-genera Naticdla, Globularia, 

 Mamillaria, Siyaretut, Naticaria, Lacuna, Leucotii). 



Sub-Family (!) Neritina. Nerits. 



Genera : Nerita, Linn, (with the sub-genus Neritoptu, Gray) ; Ncri- 

 tina, Lam. (with the sub-genera Clitlum, Velotei (Velates), Pilevlni, and 

 Navicella). (' Malacology.') 



Dr. J. E. Gray makes the Nei-itidre the sixth family of his Podoph- 

 thai ma, and places it between the Puturellida; and the Ampullariadcr. 

 Dr. (iray's Nerilidce comprise the following genera : Nerita, Pileolut, 

 C'ulana, Neritina, Clithon, Dottia, Vetatet, and Navicella. 



Adanson appears to have been the first to make known the animal 

 of a Nerita, and Cuvier afterward?, in his ' Anatomie Comparde,' gave 

 an outline of it. M. De Blainville has added some further details in 

 the zoology of the Ifranie, from individuals brought home by Messrs. 

 Quoy and Gaimard, who, in the ' Zoology of the Astrolabe,' thus follow 

 out those details. 



The Nerits are marine or freshwater animals, a modification of 

 habit which Messrs. Quoy and Gnimard think sufficient for establishing 

 a simple division between these molluscs, which Lamarck erroneously 

 j in their opinion separated into two genera Nerita and Neritina; for 

 ! their organisation Is entirely similar. Thus the Na-itn, with a com- 

 paratively thick shell, which is very rarely furnished with an epidermis, 

 nre always found in the sea; and the Neritina of Lamarck, whose 

 shell is more delicate and almost constantly covered with an epidermis, 



