The Olenellus beds are succeeded by beds containing the Paradoxides fauna, which have been found in North and South Wales, Shropshire, Scandinavia, Bohemia, Spain, and North and South America. Olenellus and its allies became extinct (or else so scarce that no relics of them have been discovered in the Paradoxides beds) before the commencement of the deposition of the strata containing the Paradoxides fauna, and few genera pass from the beds with the one fauna to that containing the other. The Paradoxides fauna existed for a considerable period, and the beds have been divided into a series of zones characterised by different species of Paradoxides, thus
Dr Hicks records the following zones in Pembrokeshire[70]:—
| Zone of | Paradoxides | Davidis |  | Menevian. |
| " | " | Hicksii | ||
| " | " | Aurora |  | Solva. |
| " | " | Solvensis | ||
| " | " | Harknessi |
[70] The order here as elsewhere is ascending, i.e. the newest deposit is placed at the top.
Dr Tullberg divides the Paradoxides beds of Scania into thirteen zones, though only a few of these are characterised by definite species of Paradoxides. The Olenellus beds have not yet been divided into zones, though this will probably be the outcome of further study[71].
[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. |
[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.