69-70

Cambrian Silurian Devon Carbonif Permian Trias L. Jura U. Jura L. Cret. U. Cret. Eocene Miocene Pliocene Recent Atlantidae 1 Hyalenidae 2—14 Woodwards numbers of Families Spiriferidae 15 Orthidae 16 Productidae 17 Orthocentidae 18—20 Ammonitidae 21—35 Belemnitidae 36—49 Hippuritidae 50—62 A

 
The accuracy of slope of line A depends on whether the Formation are equally & fairly divided which may be doubted.

All fresh discoveries will make the average Black line A slope more (for instance add 4 or 5 Fam. to Cambrian) & the starting point will be carried further back    The long step between Trias & Jurassic evidently due to few marine beds in Trias & non-discovery of Remains (mem St. Cassian beds)
}This is only an application of Woodward's principle of previous table to some large genera to all the Families.

Mr Woodwards Red. Treatises on Recent & Fossil Shells Table — (p. 415.) of all ?? Families of Recent & Fossil Shells here arranged according to periods at which they commenced: A set of steps, marking breaks, which almost everyone admits— & a great flat, broad step, when Siluria begins

How few Families have become extinct

Shows a Beginning of Mollusca It is not possible to doubt number of Forms has increased in World

70v

Geolog

/Woodward

Woodward, Samuel Pickworth. 1851-1856. Manual of the Mollusca; or, a rudimentary treatise of recent and fossil shells. 3 vols. London: J. Weale. CUL-DAR.LIB.687 vol. 1 PDF vol. 2 PDF vol. 3 PDF Abstract in CUL-DAR72.73-77.