It should be noticed here that faunas have been discovered which are possibly of earlier date than the _Olenellus_ fauna, as they do not correspond with it, or with those of newer strata. One, the _Neobolus_ fauna of the Salt Range of India, occurs in beds below those with _Olenellus_, though it is not yet clear that _Olenellus_ will not be eventually discovered associated with it, whilst the other, the _Protolenus_ fauna of Canada, is of unknown age[69]. [Footnote 69: For an account of the _Neobolus_ beds see Noetling, F., "On the Cambrian Formation of the Eastern Salt Range," _Records Geol. Survey, India_, vol. XXVII. p. 71, and for the Protolenus fauna consult a paper by Matthew, G. F., "The _Protolenus_ Fauna," _Trans. New York Acad. of Science_, 1895, vol. XIV. p. 101.] 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_ } " " _Solvensis_ } Solva. " " _Harknessi_ } [Footnote 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].