MANUAL OF CONCHOLOGY. 



Blonogrcq-jh of the Families Neritidce, Neritopsidce, 

 Adeorbiidcb, Cydostrematidce, and Liotiidce. 



Family NERITIDM 



Animal with a broad, short muzzle, and long slender tentacles, 

 with eyes on jDromineut pedicels at their outer bases, foot oblong, 

 wide in front, attenuated behind, branchia long, triangular, pointed, 

 free at its extremity, ventricle embracing the intestine, anus on the 

 right side. 



Dentition : 8-I-(3 -+ I + 3)-I-8. The middle tooth- small, sub- 

 quadrangular, second central tooth very large, transverse, sub- 

 rhomboidal, third and fourth central teeth very small ; lateral tooth 

 with reflected, simple or denticulated margin ; marginal teeth nu- 

 merous, narrow, curved, serrated. PI. 1, figs. 2, 3. 



Shell imperforate, thick, semiglobose, porcellanous, spire very 

 small, internally porcellanous, the cavity simple from the absorjD- 

 tion of the internal portion of the whorls by the animal (PI. 1, fig, 

 15), aperture semilunate, entire, the columellar lip flattened, septi- 

 form, with a rectilinear, plain or dentate margin, outer lij) rounded, 

 sharp or thickened, not reflected. 



The impression of the adductor muscle is horse-shoe shaped, open 

 in front, and is visible within the ajoerture. 



Operculum calcareous, usually subspiral, provided with projecting 

 lobes on its inner face, the inner margin forming a pseudo-articula- 

 tion with the columellar lip. 



Aquatic, although some species can live out of water ; herbivor- 

 ous. 



The Neritidse have been monographed by: 



Reeve, Conch. Icon., ix, 1855. 



Sowerby, Thes. Conch, ii, and v. 



Von Martens, Kiister's Conchylien Cabinet, 1879, 1881, 1887. 



The latter author has given for this family the most comj^lete and 

 carefully worked-up generic monographs that have lately appeared 



(3) 



