MARLSTONE. 



17 



Ammonites annulatus. M. C. t. 222. 



Area, or Cucullcea? Fragments. 

 Belemnites acutus. M. C. t. 590. 



f. 1 & 3. 



p. 114. Marlstone, Plate, f. 3. M. C. t. 254. 



- fValcottii. M. C. t. 106. 



- penicillatus. M. C. t. 590. f. 5 & 6. 



- tubularis. Phill. t. 11. f. 27- 



undulatus. Smith, Strat. System, 



Gervillia. New species. 

 Inoceramus duhius. M. C. t. 584. 

 Lucina f 



Modiola. New species ? 

 Nautilus. 



Nucula. New species. 

 Pholadomya. 



Plicatula spinosa. M. C. t. 245. 

 Trochus bisectus. Phill. t. 11. f. 27. 



The presence of this zone of clay, which in some places must have a thickness of 

 sixty or seventy feet, is marked by the outburst of water, either in the form of springs, 

 or indicated by rushes and wet ground. It forms, in fact, the retentive support of 

 all the rain-water which percolates the overlying porous strata of the Inferior Oolite, 

 and thus gives rise to the river Chelt ; to the Seven Springs, or chief sources of the 

 Thames ; to the springs which supply the Cheltenham reservoir ; to those which in 

 ancient times filled the Roman baths near Whitcomb ; and to all the streamlets which, 

 descending from the Cotteswold Hills, are tributaries of the Severn. 



The Marlstone {e. of section) is made up of alternating layers of yellow and blue marly 

 clays and sands, fox-coloured sandstone, sometimes calcareous, and beds of impure 

 limestone. 



The most prevailing fossils are— 



Avicula incequivalvis . M. C. t. 244. f. 2. Pecten cequivalvis. M. C. t. 136. f. 1. 



Belemnites penicillatus. M. C. t. 590. f. 5 &6. Terehratula concinna. M. C. t. 83. f. 6. 



Cardium truncatum. M. C. t. 553. f. 3. tetrahedra. M. C. t. 83. f. 4. 



Gryphcea gigantea. M. C. t. 391. 



Numerous ravines, by which the western sides of the Cotteswold Hills are furrowed, 

 expose this subdivision underlying the upper shale. It is also displayed in many de- 

 tached hills or outliers from the main ridge, as in Church Down, Robin Hood Hill, Bat- 

 tledown Hill near Cheltenham, Oxenton, and Bredon Hills. 



The hill of Church Down 1 , which from its insulated position presents so striking an 

 object, affords one of those examples of denudation which are frequent in the Vale of 

 Worcester and Gloucester. The quarries upon the tabular summit are covered with a 

 few feet of yellowish sandy loam, containing spheroidal concretions of hard calcareous 

 grit, called "men's heads" by the workmen. These nodules resemble those which mark 



Outliers of Marlstone. 



1 Pronounced Chosen by the inhabitants. 



