110 PATELLA-PATINA. 



The shell has the contour and texture of Helcion but is generally 

 thinner and the radiating sculpture is obsolete. 



P. PELLUCIDA Linne. PI. 51, figs. 4, 5, 9, 10. 



Shell thin, oval, elevated, the apex curved forward, near the an- 

 terior end. Surface polished, smooth except for very faint radiating 

 stride. Dark olive or brownish horn-color, reddish or blackish at 

 the apex, and usually having a few radiating interrupted lines of 

 vivid blue. Interior brownish, reddish or dusky within the cavity. 



Length 20, breadth 15, alt. 8 mill. 



Lofoten, Norway, to Cascaes Bay, Portugal. 



P. pellucida L., Syst. Nat. x, p. 783. FORBES & HANLEY, Hist. 

 Brit. Moll, ii, p. 429, t. 61, f. 34; t. AA, f. 1 (animal). P. ccerulea 

 PULT., Cat. Dorset., t. 23, f. 6. P. bimaculata MONT., Test. Brit., p. 

 482, t. 13, f. 8. P. cceruleata DA COSTA, Brit. Conch., p. 7, 1. 1, f. 5, 

 6. P. elongata and elliptica FLEM., Encyc. Edin., t. 204, f. 2, 3. 

 P. cornea POT. & MICH., Galerie Douai^ p. 525, t. 37, f. 5, 6.? P. 

 intorta PENNANT. P. minor WALLACE and P. cornea MICHAUD, 

 teste Jeffr. Patina pellucida LEACH, Moll. Gt. Brit., p. 224. DALL, 

 Amer. Journ. Conch, vi, p. 280, t. 16, f. 30 (dentition). Helcion 

 pellucidum JEFFR., Brit. Conch, iii, p. 242, t. 5, f. 4. Nacella 

 pellucida SARS, Moll. Reg. Arct. Norv., p. 119, t. 2, f. 8 (dentition). 

 P. cypridium PERRY, Conchology, t. 43, f. 6. P. Icevis PENNANT, 

 Brit. Zool. iv, p. 144, t. 90, f. 151. Patina Icevis LEACH, 1. c., p. 224. 

 Patella cornea HEEBLING, Beitriige zur Kenntniss neuer u. seltener 

 Conchyl., in Abhandlungen einer Privatgesellschaft in Boh men zur 

 Aufnahme der Mathematik, der Vaterliindischen Geschichte und 

 der Naturgeschichte, iv, p. 107, t. 1", f. 8, 1779. 



A delicate cap-shaped shell, common on fronds of laminariaB 

 throughout the seas of northern Europe. 



Var. L^VIS Pennant. PL 51, figs. 6, 7, 8. 



Shell more erect, the summit more nearly central ; solid, thick ? 

 more obviously radiately striated and having coarse concentric 

 wrinkles. Length 22, breadth 18-20, alt. 8-10 mill. 



The distribution is the same as the typical pellueida. The differ- 

 ences are the result of station, the Icevis living imbedded in the 

 stems of fuci. Specimens of all sizes may be found having the typi- 

 cal Icevis form, but frequently a Icevis is surmounted by an earlier 

 growth of the pellucida type, like the similarly caused forms 

 of P. granularis, compressa, Acmcea pelta, etc., etc. 



