91 



CHAPTER XXII. 



OF THE NAUTILUS. GENUS XIX. 



NAUTILUS. 



"Animal (Rumph. il/M.«. 1. 17. f. D). Shell univalve, with many cells; 

 the partitions arched and perforated." — Linn. 



JL HERE are a great variety of shells included in this genus, of 

 which the far greater number are only found in a fossile state ; 

 many of those found recent are very minute; the essential cha- 

 racter consists in the shell being divided into many chambers. 

 Many species are nearly wheel-shaped ; some Avith the outer 

 whorls enveloping the whole, as N. PompUius (/. 34), and 

 others with the outer whorls attached to the preceding ones, 

 leaving the inner or centre whorls conspicuous on both sides, as 

 N. Beccarii (/. 58) ; some few have the whorls a little separated, 

 but spiral, like a horn, as N. Spirula (/. 55) ; others again 

 are not spiral, but only a little bent, as N. obliquus (/. 5G) ; 

 and some quite straight, as iV. Fascia (/. 57) ; in some species 

 the whorls are cylindrical ; others are compressed, as N. Ra- 

 phamis, and consequently the shape of the mouth is various ; 

 some are smooth on the outer surface, and some are wrinkled. 

 The divisions between the chambers are generally perforated 

 by a tube, which in some species is near the centre, in others 

 near the circumference. 



N 2 . 



