THE CORALLIAN ROCKS OP ENGLAND. 



299 



seldom, if ever, found; and the other fossils have the same ten- 

 dency. The series No. 4, which Lonsdale divides into seven, and 

 the Survey into three, but which may really be divided according to 

 fancy, in different parts of the quarry, is the most important portion 

 of the section, as it contains a fine suite of fossils which serve to 

 determine the age. They are very abundant, the most characteristic 

 being Lima rigida. 



Fossils from Coralline Oolite, Highworih. 



Ammonites plicatilis (Sow.). 



perarmatus (Sow.). 



cordatus (Sow.). 



goliathus (D'Orb.). 



Belemnites Owenii (Pratt). 

 Pleurotomaria Miinsteri (Rom.) 

 Trochus daedalus (D' Orb.). 

 Cerithium muricatum (Sow.), var. 

 Littoi'ina muricata (Sow.). 

 Phasianella striata (Sow.). 

 Chemnitzia heddingtonensis (Sow.). 

 Opis Phillipsi (Mor.). 

 Sowerbya triangularis (Ph.). 

 Lithodomus inclusus (Ph.). 

 Quenstedtia laevigata (Ph.). 

 Tancredia curtansata (PA.). 

 Cuculkea corallina (Barn.). 

 Myacites decurtatus (Ph.), var. 

 Pholadomya decemcostata (Rom.). 



Unicardium depressum (Ph.). 

 Mytilus pectinatus (Sow.). 

 Gervillia aviculoides (Sow.). 

 Lima rigida (Sow.). 



lamuscula (Sow.). 



elliptioa (Whit.). 



• subantiquata (Rom.). 



Pecten fibrosus (Sow.). 



lens (Sow.). 



Avicula ovalis (Ph.). 

 Plicatula, sp. 



Anomia suprajurensis (Bav.). 

 Ostrea, sp. (cf. dilatata, Sow.). 



solitaria (Sow.). 



Exogyra nana (Ph.). 

 Ecbinobrissus scutatus (Lam.). 

 Serpula tricarinata (Sow.). 

 Cidaris Smitbii, test and spine. 



The association of Ammonites perarmatus (of the particular form 

 nere found) with A. cordatus and A. plicatilis (in the bed below) is 

 indicative of the vast mass of limestones which in Yorkshire overlie 

 the Lower Calcareous Grit proper, though belonging to the period of 

 the latter far more than to the zone of Cidaris jlorigemma ; and in 

 the "Weymouth district a similar form of A. perarmatus occurs in the 

 Osmington Oolites. The Avicula ovalis is a low form, except in this 

 district (as at Purton); and the rest, so far as they mark any particular 

 horizon in the series, are certainly characteristic of beds above the 

 Lower Calcareous Grit, such as, where well developed, are called 

 Coralline Oolite, to which age we refer these beds, carrying along 

 with them all the deposits jS"os. 2-6. The sandy and curiously false- 

 bedded mass above, is a development we have not yet met with just 

 below the Coral Rag ; but we are here entering a district of which 

 this Highworth section is more typical. 



The series so well exhibited here is exposed also in other openings 

 near the town, none of which are so full and satisfactory, but which 

 serve to demonstrate the variability in thickness and character of the 

 whole. The nearest approach to conformity with the above section 

 is seen to the north of the town, about on the line of dip, where 

 the most important beds are thickened and the corals are scattered 

 over a depth of 5 feet, a state of things which points to the same 

 conclusion as the thinning-out of the beds to the south — viz. that 

 the sediment came from the north, and the dip of the overlying Rag 



