PATELLA. 231 



surrounding the body like a wall; as distinguislied from the 

 opercular valves, or those which compose the operculum. 



PAEMACELLA. Cuv. (A little cell.) Fam. Limacinea, Lam. 



. and Bl. — Bescr. Haliotoid, internal, thin ; spire flat, consisting 

 of one or two rapidly increasing whorls ; aperture as large as 

 the whole shell, with the dorsal margins inflected. — Obs. This 

 description applies to Parmacella of Cuvier. The shell figured 

 in Sowerby's Grenera under that name is Cryptella of Webb. 

 PL xiii. fig. 256, 257, 258. 



PAEMOPHOE-US. Bl. A genus composed of EMARaiNULA 

 elongata, Auct. and other species of a similarly elongated form. 

 Australian. P. elongatus. PL xii. fig. 242. 



PAETULA. Perussac, Fam. Colimacea, Lam. Auriculacea, 

 Per. — Bescr . Conical, smooth; spire equal to the aperture in 

 length, consisting of few whorls ; aperture auriform ; outer lip 

 reflected, broad ; inner lip reflected, with a slight prominence on 

 the columella. 25 species are given in Eeeves' monograph. P. 

 australis, fig. 302. 



PASITHJSA. Lea. A genus formed of some pyramidal shells, 

 described as resembling Melania, but separated from that genus 

 on account of being marine fossils. P. striata, PL xiv. fig. 317. 



PATELLA. Linnaeus. (A dish ov platter.) Fam. Phyllidiana, 

 Lam. Eetifera, Bl. — Bescr. Symmetrical, compresso-conical/ 

 nearly regular, oblong or oval ; apex sub -central, inclining 

 towards the anterior margin; aperture oval, forming the base 

 of the shell; internal surface smooth; with a muscular im- 

 pression shaped like a horse-shoe, with the ends bending for- 

 wards, encircling and dividing the space all round, except where 



, the interruption occurs to receive the head of the animal ; ex- 

 ternal surface ribbed, grooved, striated or banded radiately. 

 Helcion is a name given to P. pellucida, fig. 230. On rocks 

 . and sea- weeds in all climates. — Obs. Patelloida differs from 



• Patella in the construction of the animal ; Siphonaria, in the 



• lateral siphon ; and Ancylus, in the oblique twist of the axis, as 

 well as in the nature of the animal. The Patellse are marine- 

 P. Oculus. PL xii. fig. 229, 230. 



