( 536 ) [Oct., 



7: GEOLOGY AND PALAEONTOLOGY. 



{Including the Proceedings of the Geological Society.) 



The energy of the Secretary of the Palaeontographical Society (the 

 Bey. T. Wiltshire) has borne fruit in the appearance this quarter of 

 another volume of the Society's Ponographs, — that for 1866, — 

 after an interval of only six months from the date of publication of 

 the one we last noticed. 



This volume opens with a second instalment of Dr. Duncan's 

 Monograph of the British Fossil Corals, in which are described the 

 Zoantharia from the Liassic zones of Ammonites planorbis and J.. 

 angidatus. These zones have recently been the subject of much 

 discussion, especially as regards then- more or less close relationships 

 with those above and below. We have recently given a summary 

 of Dr. Duncan's interpretation of the coral evidence, in recording 

 the publication of his paper " On the Madreporaria of the Infra-Lias 

 of South Wales," so on this occasion we shall confine our attention 

 to some of the author's considerations on the philosophy of zone 

 classifications generally. The Liassic and Oolitic formations have 

 been subdivided into a number of "zones," each of which is 

 characterized by, and named from, the occurrence of a certain 

 species of Ammonite. The more enthusiastic advocates of this 

 classification seem to believe that the range -of other organisms is 

 more or less co-extensive with that of the Ammonites, and that the 

 latter, being abundant in these deposits, and tolerably easy of 

 determination, afford the easiest means of identifying the zones ; it 

 has also been stated that they are the best test of horizons, because 

 their range is less uncertain than that of other organisms. Dr. 

 Duncan's researches into the distribution of the Liassic Corals have 

 not enabled him to strengthen the arguments in favour of zone 

 classifications ; on the contrary, he has been led to the conviction 

 that " the endeavour to give definite horizons to, and to correlate, 

 Saurian, Insect, Ostrea, Ammonite, and Lima beds has resulted 

 in the production of confusion instead of the reverse ; " also " that 

 no stratigraphical Palaeontology can be perfect in a classificatory 

 sense, and that zones of species may have little to do with the notion 

 of timer 



Holding this opinion the author's practice may appear incon- 

 sistent with his preaching ; but in reality he accepts the principle of 

 a zone-classification in a modified sense. " The groups of Madre- 

 poraria have a general relation to certain zones of life and to certain 

 strata; and if they are associated for the sake of a necessary 

 classification with certain Ammonite-zones, it must be understood 

 that it is only an approximative classification, and that both the 



