Geological Society of London. 93 
the term Lower Calcareous Grit, is alinost at its minimuni in tbe 
neighbourhood of Sturminster. The central limestones contain a 
moderate assemblage of the usual Corallian forms, but Cidaris 
florigemma appears confined to a rubbly bed of about 8 feet thick. 
The West Midland ränge (III.), extending from Westbury to Oxford, 
exhibits the greatest variety, and, being classic ground, contains a 
larger proportion of the type forms of the rocks. The development 
is very unequal, and the entire group is reduced to less than 25 feet 
in some places ; but where the sandy base is expanded, as in those 
districts where the escarpment faces the north, the thickness ex- 
ceeds 100 feet, occasionally falling to about 30 feet in the direction 
of the dip, with the probability of the entire mass ultimately thinning 
to a feather edge. In many places true Coral Eag is largely 
developed, usually terminating the Corallian series in an upward 
direction, or at most succeeded by a very few feet of ferruginous 
sand. Throughout the great escarpment facing the upper valley 
of the Thames, the lower arenaceous member predominates, though 
much mixed with thin-bedded sandy clays, the whole constituting 
a loose formation, which is capped by hard gritty limestone con- 
taining an abundant fauna, representative of the middle series, 
differing somewhat, on the one band, from the Eag with its partially 
Kimmeridgian character, and, on the other, from the Lower Cal- 
careous Grit, whose affinities are, of course, Oxfordian. The beds 
of this district, however, are so varied that it is irapossible to deal 
with them in an abstract. District IY. includes the Coral reef at 
Upware, 75 miles E.N.E of Oxford ; though the exposures are small, 
they are very suggestive. The limestone of the south pit is an 
excellent Coral Eag, but softer and more chalky than much of the 
Coral Eag of the West Midland district. Moreover, whilst the rock 
contains many familiär forms, and especially Cidaris florigemma, whose 
presence in abundance invariably indicates a distinct horizon, we also 
find the casts of shells, rarely or never met with in the West of 
England, but which appear common in some parts of the Continent : 
e.g. species of Isoarca, and certain species of Opis, which latter occur 
also in a portion of the Yorkshire Basin (Y.). This bears 130 miles 
N. by W. from the reef at Upware. The Corallian beds are grouped as 
a beit of rocks inclosing an oval tract of Kimmeridge Clay. There is 
more symmetry here than in the south, and the triple division of grit, 
limestone, and grit, though not absolutely true in all places, is fairly 
accurate ; most of the beds are better developed, and the contrast 
between the Coral Eag and underlying Oolites is strongly marked. 
In the Tabular Hills these Oolites constitute a double series, divided 
by a “ Middle Calc Grit,” a fact first indicated on stratigraphical 
grounds by Mr. Fox Strangways, and amply borne out by fossil 
contents. The shell beds of the Lower Limestones are, especially 
in their lower parts, charged with Brachiopoda and other forms of 
the Lower Calc Grit ; whilst the Upper Oolite, on which the Coral 
Eag reposes, contains a far more varied fauna, though singularly 
destitute of Brachiopoda. The fauna of the Eag here, as elsewhere, 
inclines to Kimmeridgian types. 
