MOLLUSCA. 797 
long tentacles not retractile, and eyes petiolate at the outside of 
tentacles. 
Sp. Navicella elliptica Lam. (Patella neritoidea L.?), Mrvuscuen Natur- 
forscher, x11. Tab. 5, fig. 1, Encycl. méth., Vers. Pl. 456, fig. 1, Buarny. 
Malacol. Pl. 36 bis, fig. 1, Pl. 48, fig. 5, &c.; fresh-water molluscs from 
the tropical regions. 
Nerita L. (in part). Shell spiral, planato-ovate or semiglobose, 
imperforate. Aperture semiorbicular, with columellar margin or 
labium dilate, transverse, truncate. Foot of animal broad, furnished 
with operculum; eyes set on petioles or tubercles at the base of 
tentacles, towards the outside. 
* Fluviatile species, with shell mostly thinner and lip edentulous. Neritina 
Lam. 
Sp. Nerita fluviatilis L., SwammMErDaM Bibl. nat. Tab. x, fig. 2, PrEIFFER 
Land- und Wasserschn. 1. Tab. 4, figs. 37—39, &e. 
* * Marine species, with shell thicker and lip often dentate. MNerita Lam. 
Sp. Nerita Peloronta L., Eneycl. méth., Vers. Pl. 454, fig. 2, Buarnv. Malac, 
Pl. 36 bis, fig. 6, &e. Species many, some fossil, 
Narica Reciuz (species of Sigaretus Lam.), Merrya GRAY. 
Shell subglobose, umbilicate, with short spire. Aperture ample, 
semiorbicular. Operculum horny. Head proboscideous; two tri- 
angular tentacles bearing very small eyes externally at the base. 
Single branchia, with triangular leaflets, contained in a large 
respiratory cavity. 
Sp. Nar. cancellata Ruciuz, Sigaretus cancellatus LAM., REcLUz, GUERIN 
Magas. de Zool. 1845, Moll, Pl. 119. Comp. on this and other species of 
this genus, all of which live in the sea, RECLUz op. cit. 
Velutina GRAY, BLAINV. 
Sp. Velutina haliotoidea, Bulla velutina Mur, Zool. Danic. Tab. tot, figs. 
1—4. (To this species O. F, MuruLEr refers Helix haliotoidea, which we 
noted above at Sigaretus.) 
Natica LAM. (Nerite umbilicate L.). Shell subglobose, umbi- 
licate, with spire short and last wreath tumid, large. Aperture 
semiorbicular, with lip oblique, edentulous, callous. Head of 
animal with broad velum; tentacles two; eyes small, sessile at the 
base of tentacles. Foot very ample. 
Sp. Natica mammilla Lam., Nerita mammilla L., Rompe. Amb. Rariteith. 
Tab. 22, fig. F, Buatnv. Malacol. Pl. 36 bis, fig. 5, &c. Species numerous, 
