BIVALVE SHELLS. 47 



hbres or filaments of which it is composed, are very tough, and of a fine 

 glossy brown colour. The ancient Romans highly esteemed articles 

 made of this byssus ; and at Naples and Palermo there are still manu- 

 factories of it. Stockings, gloves, and even a fabric resembling sarsnet, 

 are made fi-om it ; and also an imitation of broad cloths. This latter 

 stuflf is very expensive, a coat being about the value of ten pounds of 

 English money. 



The Pinna has obtained among the Italians a little reputation for 

 the practice of some of the moral virtues, in treating a small species of 

 crab with hospitality and friendship, by receiving it into the shell, and 

 defending it against its enemies. In return for this kindness, the crab, 

 like the jackal with the lion, acts the part of a provider and monitor, 

 by warning its host of the presence of its prey, or the approach of an 

 enemy. But this friendly intercourse, like the fabulous account of the 

 lion and the jackal, accords ill with the nature of the animals between 

 which it is practised. The crab, it is far more probable, is a trouble- 

 some intruder ; and, notwithstanding all the service he can repay, is 

 considered a very unwelcome guest, and is indebted for his lodging to 

 his activity and instinctive sagacity in pro\iding for his own personai. 

 safety, retaining possession from the sluggish nature of his host, rather 

 than to his kindness and hospitality. 



Genus 18.— ARGONAUTA. 



Animal a Sepia or Clio ; shell univalve, spiral, involute, 

 membranaceous, and unilocular, or consisting of a single 

 apartment or cell. 



Argonauta Argus. — The Argus Argonauta. Plate 

 VII. fig. 18. Involute, extremely fragile, white, ribbed, 

 and obsoletely striated ; the keels approximate and tuber- 

 culated, from six to eight inches in diameter. Inhabit? the 

 Mediterranean. 



The Argonauta Argus, or Paper Nautilus, is the Nautilus so famous 

 amongst the ancients, and fi-equently mentioned in the WTitings ol 

 Pliny and others. 



The singular stinicture and wondei-ful economy of this animal very 

 early attracted the attention of natm-alists. To its progressive motion 

 on the surface of the ocean mankind are indebted, it is said, for the 

 first hint of using sails in navigation. This is alluded to by Pope, in 

 tiie following lines : 



Learn of the little Nautilus to sail, 



Spread the thin oar, and catch the driving gale. 



What the pirticular organization is which enables this animal to 

 rise to the surface, or to sink to the bottom of the ocean at pleasure 

 has not yet been satisfactorily accounted for by naturalists ; whether 



