﻿Geological Society of London. 93 



the term Lower Calcareous Grit, is almost at its minimum in the 

 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 range (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 hand, 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 impossible to deal 

 with them in an abstract. District IV. 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 familiar 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 Oj)is, 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 belt 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. 



