The Morphology of ‘Stephanoceras’ zigzag

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Abstract
Many years must elapse ere I shall be able to describe Stephanoceras zigzag in the volumes of the Palæontographical Society. Meanwhile, the material which has come into my possession during the last few years throws an important light on the developments of this fossil; and such developments seem to supply a missing link in the connexion of Bathonian and Bajocian species. Not only is Stephanoceras zigzag raised from comparative obscurity to the position of probable progenitor of a large series of Bathonian species, but it is more than likely that the evidence now brought forward will be of considerable service to those engaged in studying the genealogy of the later species. For these reasons I submit the following paper to the Society. D'Orbigny's figures of Ammonites zigzag represent only small specimens of two varieties of the species. Quenstedt figures as euryodos a more quickly-coiled, more coarsely-ribbed form; but this is also small. He says it is the same as d'Orbigny's zigzag . In a former paper on Inferior Oolite Ammonites, remarked on the change of form which appears to have escaped previous notice; but the specimens then referred to were only a little larger than the Continental examples. The best figures of the species are those given by Quenstedt under the name euryodos in his last great work; but they afford no adequate idea of the developments of the fossil. It may be noted that there are distinct differences in coiling and ribbing between the specimens depicted in his fig. 5

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