«t 



SECTION V. 113 



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The body of the Shell (corpus) is that 

 part which runs from the top to the 

 extreme limits of the aperture, and may 

 with propriety be alfo called the firft whirl. 

 Plate I. Fig. 3, 4, 6, and 7. a. a. a. a, 



A whirl, turn, fpire, or wreath (Spira^ 

 Anfradus) denotes each fingle or feparate 

 turning or circumvolution. See Plate I. 

 Fig, 3, 4, i, b. 



The difpofitlon of the fpires, fays Mr. 

 Adanfon, p. xxxl. is not the fame in all 

 Shells : it varies according to the ditterent 

 plans they turn on, and they can turn on 

 four different plans, which are ; ^ . the 

 Horizontal Plan ; 2. the Cylindrick Plan, 

 or fpread on a cylindar ; 3. the Conic 

 Plan; and 4. the Ovoid Plan. From theft 

 four difpoiitions of the fpires, all the dif- 

 ferent forms or figures of Shells proceed, 



I Thefe 



