MOLLUSCA. 797 



long tentacles not retractile, and eyes petiolate at the outside of 

 tentacles. 



Sp. Navicella elliptica LAM. (Patella neriloidea L. ?), MEUSCHEN Natur- 

 forscher, xn. Tab. 5, fig. i, Encyd. meth., Vers. PI. 456, fig. i, BLAINV. 

 Malawi. PL 36 bis, fig. i, PI. 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., SWAMMERDAM Bibl. nat. Tab. x. fig, i, PFEIFFER 

 Land- und Wasserschn. i. Tab. 4, figs. 37 39, &c. 



* Marine species, with shell thicker and lip often dentate. Nerita LAM. 



Sp. Nerita Peloronta L., Encyd. meth., Vers. PI. 454, fig. 2, BLAINV. Malac. 

 PI. 36 bis, fig. 6, &c. Species many, some fossil. 



Narica KECLUZ (species of Sigaretus LAM.), Merry a 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. cancdlata KECLUZ, Sigaretiis cancellatus LAM., KECLUZ, GURIN 

 Magas. de Zool. 1845, Moll. PI. 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 MUELL. Zool. Danic. Tab. 101, figs, 

 i 4. (To this species 0. F. MUELLER refers Helix haliotoldea, which we 

 noted above at Sigaretus.) 



Natica LAM. (Neritce umbilicatce 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 mammitta L., RUMPH. Ami. Rariteilk. 

 Tab. 22, fig. F, BLAINV. Malarol. PI. 36 bis, fig. 5, &c. Species numerous. 



