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MOLLUSCA- 237 
of the older writers nearly unintelligible, althongh their 
figures are still useful to refer to. Lamark, aware of the 
imperfection of the characters of the genera of recent shells, 
as connected with this subject, and possessing a rich cabinet 
of the fossil species found in the neighbourhood of Paris, 
devoted much time to the illustration of this subject, and 
with great success, as his various papers published in the 
Annales du Museum, abundantly testify. In this country, 
Parkinson, in his work entitled Organic Remains of a For- 
mer World, has added some important illustrations of the 
genera of Lamark, and has given some good descriptions of 
the species found in our rocks. Mr. Sowerby, in his Mine- 
ral Conchology, (published in numbers), has given excel- 
lent figures of the British fossil shells; but we regret to 
add, that he has displayed too great anxiety to constitute 
species; and that the rocks in which they are found imbed- 
ed are but imperfectly characterised. But as the figures 
are well executed, they will prove highly useful to the Bri- 
tish mineralogist, by enabling him to refer to them with 
confidence, and to give names to those species which he 
meets with in the course of his investigations. 
CuEMicaL History or Fosstz Sue_is.— When we con- 
sider the elements of which shells are composed, and the na- 
ture of their combination, we might be ready to expect that 
fossil shells would differ but little instructure from recent spe- 
cies. But the case is widely different. In many instances 
the confused foliaceous structure which prevailed in the re- 
cent shell, has given place toa new arrangement of the par- 
ticles, and the fossil shell exhibits a foliated crystalline struc- 
ture. Here solution and precipitation have taken place in 
the same spot, or the results have been effected by the slow 
