74 AEGONATTTA. 



Claimed as a prior name for Monoceros, Lamarck. Chama 

 Axcinella, Auct. 



AECTICA. Sclium. Ctpeina. Lamarck. 



AREA. A flat space or disc, on any part of a shell. Ex. the 

 triangular space on tlie hinge of Area, fig. 132, and Spondyluo. 



AEENACEOUS. (Arena, sand.) Of a sandy texture, as the sand 

 tubes surrounding the bodies of some of the Annellides, named 

 Arenaria on this account. But the word is more commonly 

 used to intimate the habits of the animal, burrowing with its 

 shell in the sand. 



AEETHUSA. Montf A genus of microscopic Eoraminifera. 



AEGrONAUTA. Lamarck. Commonly called the "Paper Sailor." 

 Fam. Pteropoda, Bl. Order Cepholopoda Monotholamia, Lam. 

 — Descr. Light, thin, transparent, or nearly so, symmetrically 

 convolute, carinated by a double row of tubercles, terminating 

 smooth or tuberculated ribs radiating towards the centre ; 

 aperture large, elongated ; peritreme acute, interrupted by the 

 body whorl. — Obs. The 'exquisitely beautiful, light and delicate 

 fabrics included under the above name are inhabited by a mol- 

 luscous animal named the Ocythoe, which is provided with 

 tuberculated arms. These, hanging over the sides of the aper- 

 ture, give to the whole the appearance of a vessel propelled by 

 oars : a poetical illusion further heightened by the broad, flat 

 membranes of the two arms, which, when vertically expanded, 

 present an idea of sails. Pliny has described the Nautilus (the 

 name has been changed by the modems) as sailing gracefully on 

 the Mediterranean waters ; and Pope has versified the idea in 

 the weU known lines — 



" Learn of the little Nautilus to sail. 



Spread the thin oar and catch the driving gale." 



Scientific men have long been engaged in the interesting discus- 

 sion, whether the animal really belongs to the shell in which it 

 is found, or whether, having destroyed the rightful owner, it 

 has possessed itself of the "frail bark." It is now, however, 

 proved beyond the shadow of a doubt that the Argonaut is the 



