The Quarterly journal of the Geological Society of London . cei-as planorbis. Oiironolooical Tbrhs. y Ludwigian Age. Stepheocera-tidan Epoch. Deroceratan Age. )? Asteroceratan Age. J- Calcceratan Age. ArietidanEpoch. [I take uo responsibility for the sti-atigiaphiLttl tenns. They are only placed here interpreted from the very different views which authorities have as to tlieir use. In fa ^ I Chronographe gi5ologi(mc, 2ud cd., Ooinpte-rendu Vlfime Congr. Geol. lutan. Ziti ^ [The arenaceous Midford and Cotteswold Sands have been ranged in the Iiiferiur 0 oii;rh jnidauce;i term ditlers -riHis sul
The Quarterly journal of the Geological Society of London . cei-as planorbis. Oiironolooical Tbrhs. y Ludwigian Age. Stepheocera-tidan Epoch. Deroceratan Age. )? Asteroceratan Age. J- Calcceratan Age. ArietidanEpoch. [I take uo responsibility for the sti-atigiaphiLttl tenns. They are only placed here interpreted from the very different views which authorities have as to tlieir use. In fa ^ I Chronographe gi5ologi(mc, 2ud cd., Ooinpte-rendu Vlfime Congr. Geol. lutan. Ziti ^ [The arenaceous Midford and Cotteswold Sands have been ranged in the Iiiferiur 0 oii;rh jnidauce;i term ditlers -riHis suljilivisiu, e exception of the Sands ivhich are placed aecoiding to faunal contents, they anjation, even by the same author, accordinjj to locality.—June ICth, 1898.]rati-iaphieal and elironolo-ical, for Bathoni e ii may cjunlify Stjige or Ago.]heir aii^iUaeeous e(iuivaleiits in other places have been called iirn. treol. Soc. vr Stratigrapiiical ^by certain I>4 O qEh o Quart. Jottrn. GeoLSoc, Vol. LIV,] QCuj C3 LXJ a. LU J— CO. <Eh tfc! U. Q. O CO 5aG CO 5^ o li &3 ^ ,:=? UJ cS ^ i^ .^ UJ X -iyVd NVi Vol. 54.] DIVISIONS OF SO-CILLED JUEASSIC TIME. 451 Oertainly such generic names as Oxijnotoceras and Amaltheus areused for species of the Stepheoceratidan Epoch ; but this use isfounded only on external similarity, and not on a study of geneticaffinities.^ There seems therefore no reason to divide the Jurassic Period into more than two Epochs: the earlier dominated byammonites of the Arietidae and Hildoceratidse, which are closelyallied to one another; and the later dominated by the far morehighly developed Stepheoceratidee, in company with the Oppelidae. III. The Divisions of a Portion of Jukassic Time(with Table I). Facing p. 450 is a table of time-divisions in illustration of theforegoing remarks. It will also serve as a definite time-tablewhereby the dates of the different Jurassic species may be recorded—a matter of great importance for the study of palaeont
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Keywords: ., bookcentury1800, bookdecade1840, bookidquarte, booksubjectgeology
