1866. ] @ 98%) 
Ill. ON THE RECURRENCE OF SPECIES IN 
GEOLOGICAL FORMATIONS. 
By A. C. Ramsay, F.RS. 
Tse paper by Mr. Jenkins in the last number of this Journal, 
“On Strata Identified by Organic Remains” (an article which I 
have read with interest, and the value of which I appreciate), 
induces me to publish this brief communication with a view to point 
out that it seems to me that some of Mr. Jenkins’ arguments may 
lead to a total misunderstanding of the reasoning employed in my 
anniversary addresses to the Geological Society in 1863 and 1864. 
My chief object in these addresses was to show the connection 
between unconformity and the partial or complete change of 
marine faunas during times unrepresented by strata, and in discuss- 
ing the question whether (as had been asserted) a Silurian, a 
Devonian, and a Carboniferous fauna might all coexist in different 
areas, I stated if it were so, “that in the piles of formations” of 
Europe and America, “the chances are overwhelmingly strong, 
that im each or in some one area there might be a recurrent 
fauna, which is not the case.” 
Mr. Jenkins quotes the foregoing passage, and a little lower in 
the page he points out that I refute myself in my own address, 
because in discussing the Lower Oolites, I state, that “the majority 
of the forms that passed upwards from the Inferior Oolite lime- 
stone seem to have fled the muddy bottom of the Fuller’s-earth sea, 
and to have returned to the same area, when the later period of the 
Great Oolite began.” “Here,” says Mr. Jenkins, “ Professor 
Ramsay acknowledges a recurrent fauna.” 
Certainly there is a recurrence of forms, but only to a very 
linuted extent. The fauna of a province or of a formation means 
the collective species of the province or formation, and not a small 
percentage of them. My arguments in part are based on facts of 
that kind, viz. that in certain cases there is recurrence of species 
not in mass but in small numbers. In this case, out of about 700 
Great Oolite species, only about eighteen or twenty per cent. are 
found in the inferior Oolites beneath, whereas, from want of showing 
how I considered the question as a whole, Mr. Jenkins’ readers 
might imagine that the fauna of the Great Oolite, 7s the fauna of 
the Inferior Oolite recurrent. This is very far from being the case, 
and in my address I do not hint at anything that would lead to 
an inference so erroneous. 
But supposing that there were a recurrence of Inferior Oolite 
complete species in the Great Oolite, or on a great scale, it may 
then occur to those who remember my addresses that they are 
expected to draw the inference, that the Inferior Oolite, Fuller’s. 
VOL. III. D 
