Geological Society. 263 
PROCEEDINGS OF LEARNED SOCIETIES. 
GEOLOGICAL SOCIETY. 
June 6th, 1917.—Dr. Alfred Harker, F.R.S., President, 
in the Chair. 
The following communication was read :— 
‘ Correlation of Jurassic Chronology.’ By 8.8. Buckman, F.G.S. 
This paper owes its inception to certain discoveries made by the 
Officers of the Scottish Geological Survey during their investiga- 
tions of the Jurassic deposits of the Isles of Raasay and Skye. 
The ammonites and brachiopods were sent to the Author for 
examination, and the sequence of faunas which they disclosed 
necessarily led to comparison with results obtained in other areas — 
with Yorkshire, on which the Author had recently written a 
paleontological chapter for a Geological Survey Memoir, based 
largely on information and specimens submitted by the Survey; 
with the Dorset coast, helped by Mr. W. D. Lang’s most pains- 
taking work ; with other areas within the Authoyr’s field experience, 
helped largely by information most freely communicated by Mr. J. 
W. Tutcher. The results appeared to be so far-reaching, that 
permission was asked of the Director of H.M. Geological Survey 
to lay before the Society a synopsis of the information obtained 
through the investigations of Survey Officers; this was kindly 
accorded, and the present paper is the outcome of research thus 
originated. 
One of the principles utilized in this paper to ascertain or to 
surmise faunal sequence where precise information is defective, is 
that of what may be called ‘faunal dissimilarity ’—that is, if the 
deposits of two neighbouring localities A and B, supposedly iso- 
chronous from their sequential position, show differing faunas, it is 
a reasonable inference that the faunas are not of the same date. 
Theoretical stratigraphical correlation has usually worked along 
these lines, but the principle involved has not been recognized by 
name. Now the principle is utilized, not only in regard to neigh- 
bouring localities, but even more widely, with suggestive results. 
The paper is chiefly concerned with the Liassic Ages hitherto 
known as Domerian, Charmouthian, Sinemurian. In all of them 
there is proposed a considerable increase of the number of faunal 
horizons indicative of consecutive time-intervals, or hemere. In 
the case of the first no change of name is made; but in regard to 
the other two, subdivision seemed necessary, and each is appor- 
tioned into three Ages, as follows :— 
Proposed Names. Old Terms. 
Hiviccian. 
Wessexian. Charmouthian. 
Raasayan. 
Deiran. 
Mercian. Sinemurian. 
Lymian. 
