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stance to which I alluded ; but this form, it is to be remarked, is in 
perfect agreement with the proportions of the supposed fossil stro- 
bilus at PL IX. Fig. 1, and is to be considered 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 ob- 
servations on this curious fossil, I must refer you to that elegant 
work, Petrificata Perhiensia. 
The fossil at PI. X. Fig. 1, also serves, in my opinion, to explain 
the nature of the fossil depicted at PI. 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 or y otologists, 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 PI. IX. 
Fig. 10, serves also to render more probable, that the flattened spe- 
cimens already described, and figured at PI. I. Fig. 6 and and 
PI. 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. 
Yours, &c. 
