GINGLYMACONCHA. PINNADZ. 329 
their dorsal margin behind their umbones, which generally 
diminishes as the shells increase in size, and in old specimens 
is always more or less obsolete. 
Not knowing by what appellation I ought to distinguish 
this species, which has so many names, I at last resolved to give 
it the name of Luropea, as it is the only species yet known to 
inhabit Europe. 
FAMILY XII. PINNAD. 
Teste zequivalves elongate, posticé attenuate, infra posticé 
paululum hiantes. Valva singula impressionibus tribus mus- 
cularibus impressa. Epidermis tenuis membranacea aut cori- 
aceo-membranacea. Jigamenta duo, interius elongatum aut 
coriaceo-membranaceum. 
Animal bysso & pedis basi enascente. 
Genus 63. Pinna. 
Shells longitudinal, wedge-shaped, (anteriorly especially), 
compressed, very much attenuated behind; the umbones ter- 
minal; the valves reflexed above, and connected entirely along 
their whole length ; the elastic cardinal ligament not reaching 
the anterior margin ; the hinge toothless; the foot bearing a 
byssus. 
1. PINNA FRAGILIS. 
Shells with their valves ribbed longitudinally with obsolete 
ribs distant from one another, and abruptly attenuated behind ; 
the anterior margin somewhat longer than the exterior one 
below ; the epidermis deep horn-coloured. Length thirteen 
inches ; height anteriorly eight inches. 
Pinna fragilis, Penn. Brit. Zool. iv. t. lxix. f. 80. 
Pinna ingens, Mont. Test. Brit. 180; M. § R. Trans. Linn. 
Soc. viii. 112; Turt. Conch. Dict. 148. 
Pinna levis, Donov. Brit. Shells, t. clu. 
