No CrossRef data available.
Article contents
Observations on the genus Promicroceras
Published online by Cambridge University Press: 01 May 2009
Extract
The genus Promicroceras was separated from Xipheroceras by Dr. L. F. Spath to include Ammonites capricornoides and the Am. planicosta group. The researches of Dr. W. D. Lang on the Dorset coast have shown that the genus Promicroceras persists with relatively slight changes from the “birchi” zone up to the “ziphus” zone.
- Type
- Original Articles
- Information
- Copyright
- Copyright © Cambridge University Press 1927
References
page 76 note 1 Lang, W. D. and Spath, L. F., “The Black Marl of Black Ven and Stone-barrow”: Q.J.G.S., lxxxii, 1926, p. 144.CrossRefGoogle Scholar
page 76 note 2 The external saddle, external lobe, first lateral saddle, first lateral lobe, are referred to as ES, EL IS, and IL respectively throughout this paper.
page 79 note 1 “Studies in the Ammonites of the Family Echioceratidae,” Trueman, A. E. and Williams, D. M., Trans. Roy. Soc. Edinb., vol. liii, 1925, P. 714, fig. 8.Google Scholar
page 79 note 2 Ibid., p. 708, fig. 5.
page 79 note 3 Ibid., p. 716, fig. 12.
page 80 note 1 In comparing the developments of different ammonite species it is usual to record the stages attained at known diameters, but it appears possible that in certain cases such records may be misleading or less useful than records of the number of the whorls at which given characters are attained. Thus in Capricorn members of the Liparoceratidae ornamentation appears at a much smaller diameter than in their bituberculate descendants, but since the whorls are more swollen in these, it is probable that there is little difference in the actual number of unornamented whorls.