556 S. 8. Buckman — The Term ' Hemera.' 



the series of my dinners." But one o'clock is just what cannot be 

 said to be absent — dinner or no dinner one o'clock must arrive. 



So to return to the localities mentioned above : what has to be 

 «aid with regard to the second is that during hemera B either there 

 was no deposit or there was denudation of a deposit, according as 

 the evidence may warrant. 



Since hemera has nothing to do with zone properly speaking, so 

 it has nothing to do with subzone. It has been supposed that hemera 

 is a sort of finer division of a subzone. But it is not. Strictly 

 speaking, there should be just as many zones as there are hemeras ; 

 for the hemera is the time during which a certain piece of work, 

 namely, the deposition of what is called ' the zone,' was done. But 

 it may be said that zones coalesce. I confess to a deal of scepticism 

 about this ; for, generally, careful work shows that very attenuated 

 as the deposits may be, yet there are the zones in order of super- 

 position characterized by their distinct faunas. When there is 

 coalescence it is more of the lion and the lamb kind, with the lamb 

 inside : the earlier zone in pieces in the later one. Such is the case 

 in the Eadstock district in the Middle Lias, where the raricostatus 

 beds occur as pebbles in the armatus zone. Here the value of the 

 term 'hemera ' is seen. One cannot talk of the raricostatus zone at 

 this place, because there is really no such zone ; but one can say that 

 the strata deposited during the hemera raricostati were broken up 

 and redeposited during the hemera armati. 



Much of the trouble about zones and hemerse has arisen from 

 attempts to make the term ' zone ' a kind of ' portmanteau word,' 

 one into which several meanings were to be packed. Thus, a ' zone' 

 has been spoken of as a 'zone of life,' as a 'band of deposit,' as 

 a ' portion of geological time.' A ' zone ' has even been defined 

 as an " assemblage of organic remains " — which would make the 

 contents of a museum a ' zone.' Now in scientific work we cannot 

 have several meanings packed into one word ; and so to take away 

 the portion-of-time idea the term ' hemera ' was proposed. 



With the life-zone idea there is more trouble. In zoology the 

 zone indicates the horizontal extension of species ; it might be required 

 «nd used in this sense in geology ; but the life-zone in geology has 

 reference to the vertical range. Why cannot we call this a hio- 

 zone, using the term to signify the range of organisms in time as 

 indicated by their entombment in the strata? Thus we might 

 have the biozone of a species, of a genus, of a family, or of a larger 

 group. Thus the biozone of the Trilobita would be, say, from 

 Cambrian to Carboniferous ; the biozone of Ammonites would be 

 equal to Mesozoic time ; the biozone of an Ammonite family, 

 Arietidge, would about equal the time of the Lower Lias ; the 

 biozone of an Ammonite genus, Coroniceras, would be through 

 two or three hemerge ; the biozone of Ammonite species would 

 be about equal to a hemera. 



Then we are left with zone in its stratigraphical sense, best defined 

 by Mr. J. E. Marr. But we have no business to use it for this, 

 because of the zoological meaning which the term already has. 



