Involute.] 



MOLLUSCA. 



63 



Shell ovate, submembranaeeous, greatly depressed, with a 

 single, minute volution; whole surface concentrically wrinkled; 

 external surface covered with a silvery, iridescent epidermis, 

 exhibiting various nacred metallic hues, of blue, pink, and yel- 

 low ; aperture extending the whole length of the shell, very 

 glossy internally, and has undulations corresponding with the 

 wrinkles of the outside. Length an inch and a half; and up- 

 wards of an inch in breadth. 



This species is more membranous than P. plumula, some- 

 what more convex, with the volution and apex more prominent. 



First found on the estuary of Kingsbridge, by Colonel Mon- 

 tagu ; it has since been met with on several of the coasts of 

 Britain and Ireland. 



Family VI Phyllidiacea. 



The branchiae are situated beneath the margin of the mantle, 

 in a longitudinal series around the body. Animals respiring in 

 water. 



Genus 16. — Patella. — Linnaeus. 



Shell ovate or oblong, more or less of a conical form, desti- 

 tute of spiral convolutions ; sometimes, although rarely, pyra- 

 midal ; apex rarely central, generally placed anteriorly, with 

 its apex inclined towards the head of the animal ; concave 

 within, and the margin entire ; muscular impressions distinct, 

 and same form as the shell, placed about half way betwixt the 

 summit and the margin, interrupted in front where the head of 

 the animal is situated ; external surface striated, or ribbed in a 

 variable manner, from the apex to the base ; in the latter case, 

 the margin is variously dentated, stellated, or crenulated. 



1. Patella vulgata, pi. XX, f. 5, 12, 14, 15, and 17. 



Patella vulgata, First Ed., pi. 37, f- 5, 12, 14, 15, and 17; 

 Linne, Syst., p. 1258; Lamarck, Syst., VI, pt. 1st, p. 331; 

 Fleming, Brit. An., p. 286 ; lb., Ency., p. 65 ; Brown, Ency. 

 Brit., p. 465 ; lb., Wernerian Mem., II, p. 532 ; Montagu, p. 

 475 ; Forbes, p. 36 ; Maton and Rackett, p. 229- 



Shell subconic, oval; vertex obtuse, nearly central, or situate 

 nearest the smaller end; external surface with numerous, diver- 

 gent ribs, or striae, emanating from the apex, and terminating 

 on the margin, which is either plain, or stellated and indented, 

 as the shell may be ribbed or striated respectively ; external 

 colour various, most frequently of a dull, dusky brown, reddish- 

 brown, cr dirty yellow; inside extremely glossy and transparent, 

 variable in colour, frequently iridescent, either plain, or exhibit- 

 ing beautiful radiations of blue, purple, or brown. 



The Patella vulgata is liable to great variation in its degree 

 of elevation, general form, and external appearance, depending, 

 in a great measure, on the fineness or coarseness of its striae, 

 and the number and elevation of its ribs. In some it is covered 

 with fine, close-set, radiating stria?, crossed by irregular, inequi- 

 distant, concentric striae, or lines of growth ; in others it is 

 strongly ribbed, producing an indented margin ; these ribs are 

 always irregular in number, and the interstices with divergent 

 striae. The interior is also subject to much variety of colour ; 

 being horn-coloured, bluish-white, or yellow, and either plain, 

 or with radiations of different hues ; often with a dark brown, 

 or blackish, large, regular mark in the middle. 



The following are the more prominent varieties : 



Variety 1. Vulgata, pi. XX, f. 17. Longitudinally stri- 

 ated, or with ribs but slightly developed. 



Pennant, Brit. Zool., IV, p. 142, pi. 89, f. 145 ; Donovan, 

 pi. 14, first fig. 



Variety 2. Communis, pi. XX, f. 15. Shell depressed, with 

 sharp, subcarinated, irregular ribs, both in size and number, 

 producing an acutely angular, irregular margin ; betweeti the 

 ribs the shell is often radiated with brown or purple. This is 

 the most common form. 



Patella depressa, Pennant, p. 142, pi. 89, f. 146; Da Costa, 

 p. 3, pi. I, f. 1, 2, and 8; Donovan, pi. 14, all the figures but 

 the first. 



Variety 3. Albumena, pi. XX, f. 12 and 14. Shell de- 

 pressed ; outside with numerous, nearly equidistant, divergent, 

 rounded, but rather Jiat ribs, blunt at their external ends, and 

 always protruding considerably beyond the margin, the inter- 

 stices with strong and rather regular stria; generally of a 

 yellowish fawn-colour, and often with from four to six concen- 

 tric bands of burnt terra-sienna colour; inside of a pale bluish 

 or yellowish-white, the glazing thickened, subopaque, and not 

 very glossy, having much the appearance of albumen. 



This variety is very easily distinguished in all the stages of 

 its growth. I first noticed this very beautiful variety on rocks 

 at Color Cots, near Tynemouth, Northumberland, in 1810, and 

 T. VV. Warren, Esq., of Dublin, has lately furnished me with a 

 complete series from Portmarnock, Ireland. 



Variety 4. Conica, pi. XX, f. 5. Shell conical; its height 

 being nearly equal to its length ; with strong, radiating, blunt, 

 rounded ribs, protruding but little beyond the margin, which 

 is, in consequence, but slightly undulous. 



This variety prevails on the coast near Bamborough Castle, 

 and on some rocks at Holy Island, Northumberland. It is also 

 met with in other places of England and Ireland. I noticed it 

 in the latter country near Balbriggan, and at Killough, County 

 of Down. 



2. Patella virginea, pi. XX, f. 1, 4, and 6. 



Patella virginea, First Ed., pi. 37, f. 1, 4, and 6; Linn. 

 Gmelin, 3711 ; Patella tessulata, Miiller, Zool. Dun., pi. 12, f. 

 4, 5; Forbes, p. 36; Maton and Rackett, p. 234; Brown, Ency. 

 Brit., p. 466; lb., Wernerian Mem., p. 533; Fleming, p. 287; 

 Patella parva, Da Costa, p. 7, pi. 8, f. 11 ; Donovan, pi. 21, f. 

 2; Montagu, p. 480 ; Turton, Brit. Fau., p. 197. 



Shell thin, oval, subconic, subdepressed ; generally covered 

 with a grayish epidermis ; beneath which the surface is gene- 

 rally beautifully radiated with alternately broad and narrow pale 

 brownish-red or pink, frequently commingling in a catinated 

 manner, sometimes only visible near the margin; longitudinally 

 striated, and crossed concentrically with nearly obsolete wrin- 

 kles; vertex acute, situate nearest one end; inside smooth, 

 glossy, of a rosy or purple hue, and in some instances white. 

 Length upwards of three-eighths of an inch ; breadth a quarter 

 of an inch ; height not quite so much. It is found but rarely- 

 half an inch long. 



A local species, found in Falmouth Harbour, Whitesand Bay, 

 Cornwall ; Salcomb Bay, Devonshire ; the coasts of Northum- 

 berland and Durham ; the Friths of Forth and Clyde ; the 

 Manx coast ; and several shores of Ireland, as Dublin Bay, 

 Portmarnock, Lough Strangford, and Cove of Cork. 



