W. H. Hudleston—The Yorkshire Oolite. 393 
Relations and Distribution.—A form so prodigiously numerous as 
this cannot fail to have several relations. D’Orbigny has justly 
pointed out that, in the Inferior Oolite, J/elania coarctata, Desl., has a 
strong resemblance, though with recognizable differences. As we 
ascend in the geological scale, Chem. vittata, Phil. (G. Y. pl. vii. 
fig. 15), from the Cornbrash of Yorkshire is so near a relative that it 
requires some discrimination to make out the differences. We are 
indebted to Dr. Lycett (Suppl. to Great Oolite Mollusca, p. 14, Plate 
xxxi. fig. 10) for a good figure and description of the Cornbrash 
species. The body-whorl, instead of being rounded off at the base, 
as in Chem. Heddingtonensis, presents a double varix, whilst the other 
whorls also are rather more angular, and the sutures more deeply 
impressed. In both species, however, the early whorls are flat, and 
there exists a similar arrangement of encircling granulated lines, so 
that the absorption of the lower varix, and the modification of some 
minor points, would suffice to convert Chem. vittata, Phil., into Chem. 
Heddingtonensis, Sow. Indeed it is by no means rare to find specimens 
in the Coralline Oolite of Malton where a lower varix is discernible. 
Who shall say that, during the long interval between the Yorkshire 
Cornbrash and the Yorkshire Corallian, these alterations were not 
gradually and naturally effected in portions of the Jurassic series, of 
which in Yorkshire at least we have now no traces ? 
The variations in the Corallian species itself are very considerable. 
D’Orbigny extends the limits of the spiral angle alone from 19°—38° ; 
and certainly the specimens now figured are all about the lowest of 
these limits, though there are specimens from the Coralline Oolite of 
Malton and from the Coral Rag of Langton Wold with a wider base. 
On the other hand, the specimen, Fig. 1c, might almost come under 
the denomination of Chem. Clio, O’Orb., though I prefer to class it 
with the commoner form. Yet it’ is a matter of no small surprise 
that, amongst the enormous multitudes of Chemnitzia, so very few 
can be referred to any other of the many species described by 
D’Orbigny from the Oxfordian and Corallian of France. In North 
Germany likewise there seems to be an equal poverty of species, 
since Brauns! gives no more than three. Of these Chem. abbreviata, 
Roem., though found in the shell-bed at the top of the Lower Cal- 
careous Grit near Cumnor, has not yet been discovered in Yorkshire. 
As regards distribution in Yorkshire, Chem. Heddingtonensis, so 
characteristic of our Coralline Oolite, is first known to mein the great 
shell-bed at the top of the Lower Limestones, towards the middle of 
the Tabular range, and thence upwards throughout the Coralline 
Oolite generally, but never in the main mass of the Lower Limestones 
nor in the Passage-beds connecting them with the Lower Calcareous 
Grit. Thus with us it is absent throughout the zone of 4. 
perarmatus, or at least so rare as not to have attracted notice. 
Brauns,’? however, quotes Ch. Heddingtonensis from the Heersumer 
Schichten of North Germany, as well as from the Coralline Oolite of 
that country, whilst D’Orbigny speaks of it as common throughout 
1 Obere Jura, p. 241. 
2 op. cit. p. 177. 
