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II.—Observations on the genus Polymorphites

Published online by Cambridge University Press:  01 May 2009

A. E. Trueman M.Sc.
A. E. Trueman M.Sc.
Affiliation:
University College, Nottingham.
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Extract

In 1843 Simpson published a description of a Yorkshire Ammonite previously named Ammonites trivialis in Bean's manuscript. A few years later Quenstedt described a number of small continental Ammonites of similar character as A. polymorphus, which he further divided into the varieties lineatus, costatus, interruptus, mixtus, and quadratus. The specimens he then figured must be taken as his types; in a later work he showed many more examples which he referred to the same species; all these have small, evolute shells, but few other common characters, so that the name polymorphus was fully justified. For example, the illustrations given as Ammonites polymorphus mixtus include forms with round or square whorls, with nearly straight or with curved ribs, which may pass across the venter with or without a forward bend, or may be suppressed entirely on the venter. The specimens figured probably include young examples of several different genera.

Type
Original Articles
Information
Geological Magazine , Volume 4 , Issue 10 , October 1917 , pp. 442 - 447
Copyright
Copyright © Cambridge University Press 1917

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References

1 Simpson, M., Monog. Lias Ammonites, London, 1843.Google Scholar

2 Quenstedt, F. A., Die Cephalopoden, 1849, pp. 86–87, tab. 4.Google Scholar

3 Quenstedt, F. A., Die Ammon. de Swäb. Jura, 1885.Google Scholar

4 Haug, E., “Ueber die Polymorphidæ”: Neues Jahrb. f. Min., 1887.Google Scholar

5 Buckman, S. S., Yorkshire Type Ammonites, vol. i, No. 53, 1912.Google Scholar

1 Buckman, S. S., Yorkshire Type Ammonites, vol. i, p. xiii.Google Scholar

2 Ibid., No. 53c.

3 In litt., 08 3, 1917.Google Scholar

1 In Tate, & Blake, , The Yorkshire Lias, 1876, p. 292.Google Scholar

1 Buckman, S. S., “On the genus Cymbites”: Geol. Mag., 1894, p. 361.Google Scholar