29 
Assuming that the Pea Grit and Dogger species although 
the first of their race at present known, are not the first 
‘species that came into existence, it seems necessary to suppose 
that there are in other areas beds older than the Pea Grit which 
contain the Nerimea, but which have no representatives either 
in this country or in north western Europe. There was, I think, 
a period of greater or less duration between the deposition of 
the lower limestones of the Inferior Oolite and the Pea Grit 
of the Cotteswolds, as evidenced by the total change in the 
character of the beds, and the advent in the latter beds of many 
new forms of life, including the genus Nerinea. Perhaps no 
better evidence of such a period could be found than the 
appearance of six species of this genus in the Pea Grit, and 
their absence from the beds immediately preceding. If there 
was such a period, the Nerinea must have lived in it. 
_ According to Mr Hupueston there are triassic forms 
approaching that of the true Nerinea, and these may be found 
eventually to be the ancestors of the genus, but it is evident 
that the history of this Gasteropod is still in obscurity, the 
clearing up of which offers an ample field for investigation by 
the paleontologist; Cotteswold Geologists should embrace 
every opportunity of looking for specimens in all calcareous 
deposits anterior to the Pea Grit.* Unfortunately the sands 
and the greater part of the Upper Lias of the Cotteswolds do not 
contain many calcareous beds, so that the conditions under 
which the Nerinea lived did not to any great extent prevail in 
the Cotteswolds during the period of their deposition. It will 
be therefore very instructive if in other areas in this or other 
countries earlier calcareous beds are discovered containing the 
Nerinea ; we might then obtain a glimpse of the earlier portion 
of its history. At present we have in the Pea Grit several 
species occurring for the first time in great profusion ; and we 
may well ask, with Mr Hupiesron, how and whence did they 
come ? 
* Since this paper has been in type I have discovered fragments of two 
species in the Lower Limestone, several feet below the Pea Grit at Selsley. 
