Summary

Note on cases of representative shells that are not clearly either varieties or species.

Summary

Proportion of molluscan species to genera in various periods. The difficulty of determining species increases with the number of species per genus. Identifying species within a genus is most difficult in that period in which the genus shows its greatest development.

Summary

Thanks for Supplement to SPW’s Manual of the Mollusca [1851–6]. Praises SPW’s work. "What an amount of labour is condensed in your little volume! … I fully believe & hope that you will reap the only reward worth having, the consciousness that you have done good service to the cause of Science."

Summary

Thanks for answer to query. "I see … that there is no hope of comparing the same genus at two different periods, and seeing whether the tendency to vary is greater at one period in such genus than at another period."

Inclined to dispute SPW’s doctrine that islands are generally ancient. Doubts that they are remnants of continents.

Summary

Comments on SPW’s book [Manual of Mollusca (1851–6)].

Mentions questions he has for SPW [see 1890].

Summary

SPW and Waterhouse agree on island faunas; gives Australia and Tasmania as examples. The "stream of migration" from Asia to Tasmania.

Looks forward eagerly to the publication of CD’s "specific" researches.

Invites CD to send his memoranda [on Manual of Mollusca].

Summary

Queries from CD on the distribution of molluscan genera referring to SPW’s Manual of the Mollusca [pt 3 (1856)], with SPW’s answers.

Summary

Has reduced 20 Cyrena species to geographical varieties of one species, Cyrena fluminalis. Hooker is reducing Indian flora at the rate of 19 to 1.

Recommends W. H. Harvey’s Seaside book [1849] and Charles Pickering’s Races of man [1850].

Summary

Lists Lusitanian shells with wide ranges beyond that geographical province.

Antiquity and elevation of land mass is more important than latitude for the distribution of shells.

Summary

Thanks for information about variability in shells.

Comments on Harvey’s Seaside book [1849].

"I am growing as bad as the worst about species and hardly have a vestige of belief in the permanence of species left in me".