ZOOLOGY. 257 



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

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

 or found left dry on rocks. 



19. Naulilis. Sail-Suell. Inhabitant a Septa. 



Shell unirsLlve, convolute, smooth, composed of many cham- 

 ber or compartments, which 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; *** LongishydLaA somewhat strait. 



The Nautili hare a considerable resemblance to the last 

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

 of the ocean; but are readily distinguished by their shells 

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

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

 found in rirerSj 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 stats. 



20. Conus. Cone-Shell. Inhabitant a Slu 



Is' 



Shell univalve, convolute, turbinate ; the aperture effuse, 

 longitudinal, linear, without 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; **** Fentricose, 

 contracted at both ends ; ***** thin ; Ventricose. 



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