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narrowness, when compared with the cones of the genus Pinus. 

 This is the other circumstance to which I alluded ; but this form, it 

 is to be remarked, is in perfect agreement with the proportions of 

 the supposed fossil strobilus at PL IX. Fig. 1, and is to be con- 

 sidered as strengthening the opinion, that many genera, as well as 

 species, of vegetables, have existed, and been destroyed ; and of 

 which we have no other traces than their remains in a fossil state. 

 For some very excellent observations on this curious fossil, I must 

 refer you to that elegant work, Petrificata Derbiensia. 



The fossil at PI. X. Fig. 1, also serves, in my opinion, to explain 

 the nature of the fossil depicted at PL III. Fig. 6, and already 

 spoken of in a former Letter ; since, if the conjectures just offered 

 be right, this fossil, which has so much puzzled oryctologists, may 

 with the greatest reason be supposed to be the Amentum, or Catkin, 

 from which that kind of strobilus, the existence of which has been 

 just inferred, has been formed. The specimen depicted at PL IX. 

 Fig. 10, serves also to render more probable, that the flattened 

 specimens already described, and figured at PL I. Fig. 6 and .7? 

 and PL V. Fig. 8, are the remains of plants of the succulent tribe. 

 Every appearance which this specimen presents, serves to show that 

 it very nearly resembles the Cactus Cochenilifer, one of those plants 

 generally known by the name of Indian figs; and on which that 



curious insect, the Cochineal (Coccus Cacti) feeds and inhabits. 



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Yours, &c. 



