Manual of Style Governing Composition and Proof Reading in the Government Printing Office

by United States. Government Printing Office

16. Capitalize heads of Departments and Bureaus (of the United States Government only), but lower-case division and section officers.

17. Capitalize names of political parties: Republicans, Democrats, Tories, Home Rulers, Populists, People’s Party, Prohibition party, Prohibitionists, Farmers’ Alliance, Liberals, etc.

18. Capitalize names of societies: Odd Fellows, B’nai B’rith, etc.

19. Capitalize names of geological ages, eras, and periods:

Ages:

Archæan

Paleozoic

Cenozoic

Eras:

Lower Silurian