Note 512 — Chapter XI · THE LOGARITHMIC SPIRAL
Reading edition
Alcide D’Orbigny, Bull. de la soc. géol. Fr. XIII, p. 200, 1842; Cours élém. de Paléontologie, II, p. 5, 1851. A somewhat similar instrument was described by Boubée. in Bull. soc. géol. I, p. 232, 1831. Naumann’s Conchyliometer (Poggend. Ann. LIV, p. 544, 1845) was an application of the screw-micrometer; it was provided also with a rotating stage, for angular measurement. It was adapted for the Study of a discoid or ammonitoid shell, while D’Orbigny’s instrument was meant for the study of a turbinate shell.