No. 17. PINNA. 



Nacre, or Sea-wing. Inhabitant a Limax. 



This shell, which forms the connecting link between the bivalve and the 

 univalve, is so formed as to possess equal claims to either division. The 

 Pinna are all inhabitants of the ocean, in the sand and mud, on the shore of 

 sheltered bays: they may be often obtained standing erect, or affixed by their 

 beards, to rocks and stones. A bed of these shells was discovered a few years 

 ago, in Salcomb Bay, near Kingsbridge, Devonshire, in England, by Colonel 

 Montague. The animals are accounted a very palatable food, but require at 

 least five or six hours' stewing. 



The Pinna is sub-bivalve, fragile, erect, gaping, and furnished with a bys- 

 sus or beard, hinge without teeth, the valves uniting into one. This genus is 

 well defined: the shell of which it consists is wedge-shaped, or somewhat of 

 a triangular form, widening from a pointed top to a very broad end: the hinge 

 is inarticulate, the two valves being united in that by a part, and thus forming 

 what Linnaeus truly terms it, a sub-bivalve, for it is not strictly two valves being 

 thus connected. Pinna is derived from the Latin, signifying a pin, &c. 



The Pinna? are termed by some Writers Silk Worms of the Sea, from the 

 quantity of fine strong byssus which the animals produce: it consists of a 

 silky filament of a brown color, and which is easily woven into small articles 

 of dress. There is a considerable manufactory of this at Palermo. These 

 animals are found in smooth water, and in bays. The Mediterranean pro- 

 duces a considerable number. They are also discovered in the Indian, 

 American, Atlantic and European Oceans, as well as in the Adriatic or Red 

 Seas. The byssus is thus produced by the animal: — on any sudden emer- 

 gency, it darts out an extensive member, and discharges from its lip a drop of 

 gluton, which, by the drawing back of the same organ, immediately forms a 

 silky thread, till by a repetition of this simple operation, a thick tuft is at 

 length completed. 



The Earl of Shaftesbury has referred to the production of these industrious 

 insects, in this elegant manner: " How shining, strong and lasting are the 

 subtle threads spun from their artful mouths! Who besides the All- wise 



