Continues discussion of Dana’s Geology [1849]. Comments on dikes of Hawaiian volcanoes and Dana’s view of craters of denudation. Compares role of sea and rivers in forming valleys. Criticises Dana’s treatment of CD’s account of coral reefs.

Comments on AC’s experiments on Phlox and Mimulus.

Discusses his accounts.

Discusses the new genus, Alcippe, described by AH ["Notice of the occurrence on the British coast of a burrowing barnacle", Ann. & Mag. Nat. Hist. 2d ser. 4 (1849): 305–14]. Comments on Lithotrya, Clitia, and Anatifa. Discusses cirripede larvae. Asks which Mollusca specimens AH wishes to borrow.

CD is distressed that JS’s shipment of fossils has been lost: "of all the Cirripedes in the world, I most wish to dissect the Alepas squalicola". Welcomes JS’s offer to send some northern recent species. CD finds great confusion in the current classification of cirripedes in British museums; different genera are made into one species, mere varieties are made into distinct species. If JS would give him some named common northern species, it would be of great assistance.