It is curious that some of the most common fossil shells are not now
known in their recent state, as the cornua ammonis; and on the contrary,
many shells which are very plentiful in their recent state, as limpets,
sea-ears, volutes, cowries, are very rarely found fossil. Da Costa's
Conchology, p. 163. Were all the ammoniae destroyed when the continents
were raised? Or do some genera of animals perish by the increasing power
of their enemies? Or do they still reside at inaccessible depths in the
sea? Or do some animals change their forms gradually and become new
genera?]

[_Echinus. Nautilus_. l. 67, 68. See additional notes, No. XXVII.]

[_Pinna. Cancer_. l. 70. See additional notes, No. XXVII.]

[_With worm-like beard_. l. 71. See additional notes, No. XXVIII.]

[_Feed the live petals_. l. 82. There is a sea-insect described by Mr.
Huges whose claws or tentacles being disposed in regular circles and
tinged with variety of bright lively colours represent the petals of
some most elegantly fringed and radiated flowers as the carnation,
marigold, and anemone. Philos. Trans. Abridg. Vol. IX. p. 110. The Abbe
Dicquemarre has further elucidated the history of the actinia; and
observed their manner of taking their prey by inclosing it in these
beautiful rays like a net. Phil. Trans. Vol. LXIII. and LXV. and LXVII.]

[_And drop a pearl_. l. 84. Many are the opinions both of antient and
modern concerning the production of pearls. Mr. Reaumur thinks they are
formed like the hard concretions in many land animals as stones of the
bladder, gallstones, and bezoar, and hence concludes them to be a
disease of the fish, but there seems to be a stricter analogy between