PATELLA. LIMPET. 135 



Shell thin, semitransparent, white or yellowish-white 

 but not glossy, fiat, thin, orbicular and entire at the margin, 

 about which it is often a little rough with circular rows of 

 minute tubercles, and rising from the centre into a conic- 

 pointed crown, which appears to consist of a single protube- 

 rance upon the top of which is a mammillary point, which in 

 perfect specimens forms a single volution : inside smooth, 

 glossy-white, furnished with a broad flat thin appendage, 

 which is placed obliquely near one side, and a little twisted 

 spirally: length about half an inch ; not so much in height. 



On the inside of oyster-shells, in the west of England, 

 and Dublin bay. v. v. 



2. Patella orbiculata. Orbicular Limpet. 

 Walker, pi. 1. f. 16. 



Shell orbicular, flat, opake, white, with the margin re- 

 gularly toothed ail round : crown central : inside with a 

 transverse partition in the middle : minute. 



On the Sandwich coast ; very rare. 

 B. With the crown entire, 3 to 16. 



3. Patella vulgata. Common Limpet. 



Lister, pi. 535. f. 14 Pennant, pi. 92. f. 1 Da Costa, 

 pi. 1. f. 1, 2, and 8 Donovan, pi. 14 Dorset Cat. pi. 23. 

 f. 1, 2, and 8. 



Shell with fourteen or more raised tubercled ribs and in- 

 termediate fine lines, forming as it were obsolete angles 

 which cause the margin to be indented, generally conic, but 

 often flattish : color rufous brown, purplish, reddish or horn- 

 color, often dull white with a plain margin when worn, and 

 of an oblong or roundish shape : crown nearly central and 

 more or less elevated ; inside glossy, white, flesh-color, 

 blue, purplish, or horny, often iridescent and beautifully ra- 

 diate with yellow and chesnut; the bottom white or blueish* 

 white, and generally opake : length reaching to two inches, 

 and one and a half in height. 



This shell puts on so great a variety of appearances, that 

 it is impossible minutely to pourtray them all : sometimes 

 it is extremely conic, often much depressed ; sometimes 

 strongly tubercled longitudinally, with intermediate fine 

 smooth lines j frequently appearing as if finely and regu- 

 N 2 larly 



