12. Where compass directions are contracted, use the forms NE., NNW., etc.
13. Use “F.” for Fahrenheit and “C.” for centigrade when temperatures are given.
14. Use “Pl.” and “Fig.” for plate and figure before roman numerals, as Pl. VI, Fig. XII; “pl.” and “fig.” before figures, as pl. 6, fig. 12.
15. Use “Rev. Stat.” for Revised Statutes, and “Stat. L.” for Statutes at Large, in citations.
16. Set abbreviations for section, township, range, etc., thus: SE. ¼ sec. 5, T. 9 N., R. 2 E.
17. Use “loc. cit.” for loco citato; “op. cit.” for opere citato; “sp. gr.” for specific gravity, and “sp. nov.” for species nova.
18. Where the metric system of weights and measures is used, follow copy, and where contractions occur use roman lower-case or superior letters, according to indicated preference, as “cm. or cm,” for centimeter; “mm. or mm,” for millimeter; “c. c. or cc,” for cubic centimeter.
19. After “per cent” and “viz” omit the period.
20. References to Congressional documents: House Ex. Doc. No. 6, Forty-seventh Congress, second session; Senate Mis. Doc. No. 10, Forty-sixth Congress, first session.
21. Use “v.” (versus) in all cases except “fol.” and “fol. lit.”