104 
ORGANIC REMAINS. 
on the same strata, in the south of England. If the fossils of the Kim- 
meridge clay could be collected in sufficient variety, possibly we might 
find in Yorkshire, as in the vicinity of Weymouth, some species which 
are also found in the oolite ; but this must only be expected at the base 
of the clay in stony layers, almost in contact with the rock. — (See Smith’s 
account of the Ivimmeridge (Oaktree) clay in strata identified, p. 18.) 
Secondly, it is interesting to observe how large a proportion of the 
remains of mollusca are common to both the calcareous grit and the 
coralline oolite in Yorkshire and Oxfordshire. The most remarkable 
of these species are the following : viz. astraea favosioides, a. micras- 
tron, a. arachnoides, a. tubulifera, meandrina, cidaris florigemma, c. 
intermedia, c. monilipora, clypeus clunicularis, c. dimidiatus, c. semi- 
sulcatus, corbis lee vis ? astarte ovata, cardita similis, gervillia avicu- 
loides, plagiostoma keviusculum, p. rigidum, p. rusticum, pecten 
in«equicostatus, p. viminalis, ostrea gregarea, turbo muricatus, trochus 
granulatus, turritella muricata, melania Heddingtonensis, ammonites per- 
armatus, a. vertebralis, belemnites abbreviates ? This result is also per- 
fectly in unison with the conclusion which suggests itself, in considering 
the other geological relations of these rocks : for the frequent alternation 
of calcareous grit and limestone beds at the bottom of the oolite, (see the 
account of Filey Brig, page 49,) and the recurrence of calcareous grit 
above the oolite, leave no doubt of the propriety of uniting these rocks 
into one group or subformation. The principal differences between the 
two rocks arise from the prevalence of remains of the classes zoophyta 
and radiaria, and the presence of melanias, turbines, and turritella in the 
upper beds of the coralline oolite* Besides a considerable number of spe- 
cies which are so rare that we cannot pronounce whether they are pecu- 
liar to the stratum, or to the quarry that furnished them, as trigonellites 
antiquatus, avicula elegantissima, and a. tonsipluma, there are several 
common to this rock, but not yet found in the calcareous grit, as the 
* A striking proof of the accuracy of this generalization is afforded by Mr. Murchison s excel- 
lent account of the carboniferous and calcareous rocks in Sutherland ; for among the fossils which 
he enumerates from the calcareous grit of Braambury, none of these are mentioned. 
