88 



CHAPTER XX. 



OF THE PINNA. GENUS XVII. 



PINNA. 



" An'imAl a Umax. Shell nearly bivalve, brittle, upright, throwing out a 

 bearded byssus ; hinge without teeth ; valves united in one." — Linn. 



The shells of this genus are broad at the upper end, tapering 

 to a blunt point below (;j/. 4./. 51) ; they are thin and mostly 

 rough ; they do not shut close at the broad end, and are some- 

 what similar in texture to the shell of the Muscle. The valves 

 are equal and nearly flat ; they are connected by a very long 

 external cartilage, extending about half the length of the shell 

 from the pointed end upwards. There is not any appearance 

 of teeth at the hinge. There must be surely some mistake in 

 Linnaeus's calling the animal a Limax ; it appears to differ 

 but little from the animal of the common Muscle (see Adan- 

 son, p. 212) ; it fixes itself by a large byssus, of which a kind 

 oisilk gloves are made at Palermo (see Spectacle de la Nature, 

 vol. 1, p. 141). 



Linnaeus has described 8 species, Gmelin has added 10, and 

 Dr. Turton none. Total, 18. 



Lamarck has made no alteration in this genus. 

 Pinna. Shell longitudinal, wedge-shaped, pointed at the base, 

 open at the upper end, and fixing itself by a byssus ; the 

 hinge without teeth ; the cartilage external, very loi^ 

 (see Pinna rudis Linn. f. 51). 



