NAUTILUS. 199 



umbilicus nearly filled up by a vitreous deposition of the inner 

 lip ; spire obtuse. N. aurantia. Mart. 189. f. 1934, 1935." Sw. 

 p. 345. 



NAVICELLA. Lam. (A little skip.) Fam. Neritacea, Lam Hemi- 

 cyclostomata, Bl. — Descr. Transversely oval, symmetrical, smooth; 

 aperture entire, oval ; dorsal surface convex ; outer lip thin ; 

 inner lip flat, straight edged ; spread over the front surface of the 

 body whorl, and sometimes hiding the apex ; apex incurved ; 

 operculum testaceous, flat, sub-quadrate, with a lateral articula- 

 tion. — Obs. This well known genus, of which there are several 

 species, is named Cimber by Montfort. The shells are brought 

 from India, the Isle of France and the Moluccas. Fig. 323, N. 

 elliptica. 



NAUTELLIPSITES. Parkinson. A generic name proposed to 

 include such species of Nautilus as have been compressed, so as to 

 assume an oval instead of a round form. ' The genus Ellipsolites 

 of De Montfort consists of species of Ammonites similarly 

 deformed. 



NAUTILACEA. Bl. The fifth family of Polythalamacea, Bl, the 

 shells of which are described as more or less discoidal, com- 

 pressed, symmetrically convolute ; the last whorl much longer 

 than the others ; which are entirely hidden beneath it and 

 advancing beyond the last but one, so as constantly to form a 

 large oval aperture, which is always, however, modified by the 

 last whorl. The septa are united in the greater number of 

 instances and pierced by one or more (?) siphons. This family 

 contains the genera Orbulites, Nautilus, Polystomella and Len- 

 ticulina. 



NAUTILACEA. Lam. The sixth family of Polythalamous Cepha- 

 lopoda, Lam. containing the genera Discorbites, Siderolites, 

 Polystomella, Vorticialis, Nummulites, Nautilus. To these may 

 be added Simplegas and Endosiphonites. Fig. 472 to 476. 



NAUTILUS. Auct. {A little boat.) Fam. Nautilacea, Lam. and 

 Bl. — Descr. Convolute, discoid, chambered, symmetrical ; spire 

 partly or entirely concealed by the last whorl ; aperture modified 



