138 PATELLA. LIMPET. 



of the crown, or inside markings. The error originated in 

 Da Costa, who considered the P. laevis to be the old shell of 

 P. pellucida : and this error has heenmore or less confusedly 

 continued ever since. Even Mr. Dillwyn, who makes them 

 distinct, has quoted the figure 6, in Da Costa's first plate, 

 and which is the P. laevis, for P. pellucida ; and Donovan's 

 plate 3. fig. 1. which is P. pellucida, for P. laevis. 

 On the leaves of Fuci. v. v. 



S. Patella lacustris. River Limpet. 



Lister, pi. 141. f. 39 Da Costa, pi. 2, f. 8 Donovan, 

 pi. 147 Dorset Cat. pi. 22. f. 8. 



Shell oval, rather conic, very thin, transparent, horn-co- 

 lor, covered with a dusky green or dark rough skin, white 

 when dead, very obscurely striate longitudinally with often 

 a few transverse wrinkles, glossy within and white or 

 blueish : crown not quite central, slightly hooked, ending 

 in an obtuse point : length three-eighths of an inch , breadth 

 a quarter ; height not a quarter. 



In rivers, attached to stones, v. v. 



9. Patella Extinctorium. Extinguisher Limpet. 



Shell exactly conic, brownish horn-color and rather 

 rough, semitransparent, with a few irregular circular wrin- 

 kles ; the point rather obtuse, quite erect and central, 

 without curvature or apparent volution ; the base orbicu- 

 lar, with the margin thin and plain ; inside glossy brown- 

 ish-white : diameter of the base the tenth of an inch j 

 height about a third more than the diameter. 



A living specimen of this curious and very distinct mi- 

 nute Patella we took from a mass of the Serpula tubularia* 

 trawled up at Torbay. Its figure exactly resembles a com- 

 mon extinguisher: and independently of its regularly conic 

 shape and comparatively contracted base, it may be known 

 from the P. Chinensis by the want of internal appendage 

 or lip. v. v. 



10. Patella oblonga. Oblong Limpet. 



Donovan, pi. 150 Dorset Cat. pi. 18. f. 20*, and pi. 22. 

 f. 8. a. 



Shell oblong> contracted in the middle, very thin and 



transparent, 



