i28(> MOLLUSC A. BRANCHIFERA. Valvata. 



Fkm. Phil. Zool. ii. 470. t. iv. f. 2 — Frith of Tay. 

 Length about an inch, slender, pointed behind, rounded in front, of a pink 

 colour. Anteal tentacula, shorter than the superior ones, which have the 

 eyes behind. Three filiform branchia? in each bundle. 



Gek. XLI. valvata. — Shell spiral; aperture circular, 

 operculated. Branchiae single, plumose issuing from the 

 neck. 



151. V. cristata. — Shell depressed, of three or four whorls, 

 nearly flat above, concave below. 



Mull. Verm. ii. 198. — Helix cornea quatuor anfractibus apertura rotun- 

 da. Walk. Test. Min. 5. t. i. f. 18 — Helix exist. Mont Test. Brit. 

 460. fig. i. f. 7, 8. — In rivers and ditches, England. 

 Breadth about Jgth of an inch, light horn-coloured ; whorls rounded, in- 

 creasing gradually, slightly wrinkled across ; the central cavity exposes all 

 the whorls ; aperture attached to the body-whorl, but not interrupted by it ; 

 operculum spirally striated. Animal dusky, tentacula three, two placed in 

 front, at the base of which are the eyes, and one on the right side, corres- 

 ponding with the branchia, setaceous and produced. Front emarginate. 



152. V. piscinalls. — Shell turrited, whorls four or five, round- 

 ed, with a large central cavity. 



Nerita pis. Midi. Verm. ii. 172 — Turbo tribus anfractibus, umbUicatus 

 apertura subrotunda. Walk. Test. Min. 15. t. ii. f. 50 — Turbo fonti- 

 nalis, Mont. Test. Brit. 348. t. xxii. f. 4 — In lakes and slow running 

 streams, common. 

 Breadth and height about a quarter of an inch. Whorls increasing rapid- 

 ly, yellowish-brown, distinctly stiiated across ; central cavity distinct, but 

 not large ; apex obtuse ; aperture orbicular, lip thin, slightly attached to the 

 body -whorl ; operculum spirally striated, with a central knob. Animal like 

 the last. 



Gen. XLII. PATELLA. Limpet.— Shell entire, conical; 

 snout with two pointed tentacula, with eyes at the base ; 

 tongue long, strap-shaped, covered with three rows of in- 

 terrupted reflected short spines. 



1 53. P. vulgata. Common Limpet. — Shell with about four- 

 teen obsolete angles ; apex nearly centra], blunt. 



P. ex livido cinerea, striata, List. An. Ang. 195. ; Conch, t. dxxxv. 14. 

 P. vul. Linn. Syst. i. 1258. Mont. Test. Brit. 475 — Conmion on 

 rocks, near low water-mark. 

 Shell sometimes 24 inches long, and 2 inches broad in the aperture, and 1^ 

 inch in height. It is subject to great variation in the height of the apex, 

 the elevation and number of the markings, the form of the aperture, and the 

 thickness. Foot oval, snout subcylindrical ; margin of cloak fringed ; bran- 

 chial circle complete — This species is of great value as a bait in our fisheries, 

 and even as an article of food. 



154. P. intorta. — Shell with numerous rough ribs; apex 

 prominent, submarg-inal, and slightly decurved. 



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