GASTEROPODA. 



141 



Nerita, L. Nerite. 



EUjm. Nerites, a sea-snail, from nereis. 



Ti/pe, N. ustnlata, PL IX., fig. 35. 



SheU thick, smootli or spirally grooved ; epidermis horny ; outer lip 

 thickened and sometimes denticulated within ; columella broad /A 



and flat, with its inner edge straight and toothed; operc. fh. j\ 



sheHy, fig. 86. -W /'A I 



Distr., 116 sp. Nearly all warm seas. W. Indies, Red "^if^^^j 

 Sea, Zanzibar, Philippines, Australia, Pacific, W. America, ^-V^XJs^ 

 (Cuming). Fig. 86.* 



Fossil, 60 sp. Lias — . Brit. &c. The palseozoic nerites are referred by 

 D'Orbigny to turbo, natica, &c. N. haliotis is a pileopsis. 



Sub-genera. Neritoma, Morris, 1849. N. sinuosa. Shy. Portland stone, 

 Swindon. (Mus., Lowe). SheU ventricose, thick; apex eroded; aperture 

 with a notch in the middle of the outer lip. Casts of this shell are common, 

 and exhibit the condition of the interior characteristic of all the nerites ; it 

 was probably fresh-water. 



Neritopsis, Grateloup. N. radula, PI. VIIL, fig. 9. Shell like nerita ; 

 inner lip with a single notch in the centre. 



Distr., 1 sp. Pacific. Fossil, 20 sp. Trias ? Brit., France, &c. 



Velates, Montf. N. perversa, Gm. PL IX., fig. 36. Inner lip very 

 thick and callous ; outer lip prolonged behind, and partially enveloping the 

 spire. 



PiLEOLUS, (Cookson) J. Sowerby. 



Etym., p)ileolus, a little cap. 



T>/pe, P. plicatus, PL IX., fig. 37, 38. 



Shell limpet-like above, with a sub-central apex ; concave beneath, with a 

 smaU semi-lunar apertm-e, and a columeUar disk, surrounded by a broad coij- 

 tinuous peristome. 



Distr., marine ; only known as fossils of the Bath oolite, Auclifie, and 

 Mincliinhampton, 3 sp. P. neritoides is a neritina. 



Neritixa, Lara. Presh-water nerite. 



E.i'amples, N. zebra, PL IX., fig. 39. N. crepidularia, PL IX., fig. 40. 



Shell rather thick at the aperture, but extensively absorbed inside ; outer 

 lip acute ; inner straight denticulated ; operc. shelly, with a flexible border ; 

 slightly toothed on its straight edge. 



Animal like nerita ; lingual teeth; — median, minute; laterals 3, 1 large, 

 sub-triangular, 2, 3, minute ; uncini about 60, first very large, hooked, denti- 

 cidated ; the rest equal, narrow, hooked, denticulated. 



The neritiuffi are small globular shells, ornamented with a great variety 

 of black or pm-ple bands and spots, covered with a polished horny epidermis 



* Fig. SG. Operculum of N. peloronta. W. Indies. 



