ZOOLOGY. 257 



perfect, as the instant they are disturbed, they disappear, and 

 and are only accidentally brought up in the nets of fishermen, 

 or found left dry ou rocks. 



19. Nauti'is. SAiL-SiiELr,. Inhabitant a (Se/jza. 



Shell aniralve, convolute, smooth, composed of many chant' 

 bers or compartments, vrhich are perforated and con- 

 nected by a thin testaceous pipe. Plate 5, fig. 19. 



These shells are separated into three families, * Spiral, 

 with the spines connected; ** Spiral, with the Whorls 

 distinct; *"* Longish, ^.xxdi somewhat strait. 



The Nautili have a considerable resenblancG to the last 

 genus, like which, they are often seen floating on the surface 

 of the ocean ; but are readily distinguished by their shell« 

 having many, and the former genus only one chamber. The 

 larger kinds are entirely marine, some of the smaller species are 

 found in rivers^ brooks, and ponds, frequently adhering to the 

 leaves and stems of aquatic plants, and to pieces of wood; 

 others are found only in a fossil state. 



20. Conus. Coxe-Shell. Inhabitant a Slug. 



Shell univalve, convolute, turbinate ; the aperture effuse, 

 longitudinal, linear, vfithout teeth, entire at the base; 

 columella smooth. Plate 5, fig. 20. This genus is divi- 

 ded into five families; * Spire truncate, or flat; 

 ** Piriform; *** Elongated; **** Ventricose, 

 contracted at both ends ; ***** thin ; Fentr lease. 

 s 



