27 
of a mile; so far however as my observation has extended, the 
various species are usually confined to particular zones,—but two 
species are found both in the Shelly beds and White Limestone 
of the Great Oolite. 
Mr Houpixsron, in his papers on “The Palzontology of the 
Yorkshire Oolites,”’* has alluded to the Genesis of the Nerinea. 
He apparently regarded N. cingenda, found in the Dogger, as 
the first of its kind in England, and anterior in time to the 
appearance of the genus in France and Germany. He mentioned 
the same species as occurring in the Northampton Sand and in 
the Pea Grit of Leckhampton, according to the identification 
of Mr Suarre and Dr Wricut respectively. In consequence of 
‘the imperfect condition in which the Yorkshire shells are pre- 
served it seems rather uncertain whether the fossils found in the 
Dogger are confined to this single species. From comparison 
with the Cotteswold beds on the same horizon the inference is 
that there are several species in the Dogger, and I think it 
exceedingly probable that further researches will disclose the 
fact. 
Mr Hupueston asks how and whence did these curious 
shells come? and again, does the evidence at present in our 
possession lead us to suppose that they appeared almost simul- 
taneously along the whole line, or earlier in one place than 
another? The first of these questions will be found very 
difficult to answer; but, as regards the second, if we consider 
that the Dogger and the Pea Grit are on the same horizon, 
there is less difficulty in answering it, and it may be replied, 
with something approaching to certainty, that the genus 
appeared about the same period in the Dogger, the North- 
ampton Sand, and the Cotteswolds, although I think that the 
Cotteswolds have the priority, because in the Dogger the 
Nerinea bed is near the top of the series, while in the Cottes- 
wolds it is near the bottom. But how and whence did they 
come? If the first appearance of the genus had been repre- 
sented by a single species, as was at one time supposed, and 
the species had been of a simple character as regards its 
* Geol. Mag. Dec. 3, Vol. I., No. 3, p. 109. 
