[Footnote 71: The _Paradoxides_ fauna is described in the following works: Britain, Hicks, H. and Salter J. W., _Quart. Journ. Geol. Soc._, vol. XXIV. p. 510, XXV. p. 51, XXVII. p. 173, and Hicks, H. and Harkness, R., _ibid._ vol. XXVII. p. 384; Scandinavia, Angelin, N. P., _Palæontologia Scandinavica_; Brögger, W. C., _Nyt Magazin for Naturvidenskaberne_, vol. XXIV., Linnarsson, G., _Sveriges Geologiska Undersökning_, Ser. C. No. 35; Bohemia, Barrande, J., _Système Silurien du centre de la Bohême_; Spain, Prado, C. de, "Sur l'existence de la faune Primordiale dans la chaîne Cantabrique suivie de la description des Fossiles par MM. de Verneuil et Barrande," _Bull. Soc. Geol. France_, 2 Series, vol. XVII. p. 516; America, Walcott, C. D., _Bull. U. S. Geol. Survey_: "The Cambrian Faunas of North America," and Matthew, G. F., _Trans. Roy. Soc. Canada_, 1882 and succeeding years.] The strata with _Paradoxides_ are succeeded by those with the _Olenus_ fauna, characterised by the genus _Olenus_ and a large number of allied genera or sub-genera as some prefer to term them. The genus _Olenus_ (_sensu stricto_) is very abundant in the lower part of the series, whilst the allied forms are more abundant in the upper beds. The genus _Paradoxides_ and its associates disappeared before the deposition of these strata containing _Olenus_ and its allies, and indeed the complete change in the character of the faunas in Europe is very remarkable. The _Olenus_ fauna has been found in North Wales, Pembrokeshire, Warwickshire, Worcestershire, and abroad in Scandinavia and Canada. It is interesting to note among the fossils of the _Olenus_ beds the occurrence of a graptolite which is associated with _Olenus_ in Scandinavia; this is the earliest recorded appearance of a group which is destined to play so important a role amongst the fossils of the succeeding system[72]. The following zones have been detected by Dr S. A. Tullberg amongst the _Olenus_ beds of Scania:-- Zone of _Acerocare ecorne_. " _Dictyograptus flabelliformis_. " _Cyclognathus micropygus_. " _Peltura scarabæoides_. " _Eurycare camuricorne_. " _Parabolina spinulosa_. " _Ceratopyge_ sp. " _Olenus_ (proper). " _Leperditia_. " _Agnostus pisiformis_. [Footnote 72: For descriptions of the _Olenus_ fauna consult the following:--Wales, Belt, T., _Geol. Mag._ Dec. I. vol. V. p. 5, and Salter, J. W., _Decades Geol. Survey_, Decade II. Pl. IX. and Decade XI. Pl. VIII.; Scandinavia, Angelin, N. P., _Palæontologia Scandinavica_, and Brögger, W. C., _Die Silurischen Etagen 2 und 3 im Kristianiagebiet und auf Eker_; Canada, Matthew, G. F., "Illustrations of the Fauna of the St John Group, No. VI.," _Trans. Roy. Soc. Canada_, 1891.]