PREFACE. IX 



Every system of natural bodies should assume, 

 for its basis, but one principle ; and this should be 

 drawn from the most essential characteristics of the 

 bodies under arrangement. Hence, form is pointed 

 out as furnishing the only genuine principle, on 

 which the classification of reliquia can be estab- 

 lished. V. p. 182. also p. 199, Note. 



It may be here objected, that I have not my- 

 self adhered to the principle now proposed^ as both 

 the prototype, or original body, and the soil of the 

 reliquiiim are brought forwards to characterize the 

 divisions of the system, given at the end of this 

 work. But, with respect to the prototype, it is 

 sufficiently apparent, that this is only to be deter- 

 mined according to the form of the extraneous fos- 

 sil ; consequently, in this instance, the principle of 

 arrangement proposed is strictly followed up : and, 

 in regard to the soil, I have to remark, that it is 

 never stated, except as a secondary and factitious 

 character a mere geological help to discriminate 

 a division, not a genuine distinction. 



4. TJie primary divisions of the arrangement 

 (orders, genera, &c.J should agree with such na- 

 tural divisions of plants and animals, as arc deter- 

 ininable by the form of the fossil subjects. 



