106 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 17, 



undergone many modifications since the liassic view has been taken 

 of it. Hence, in the Oolitic sands, and the equivalent beds, we 

 may mark an oscillation, the effect of which was the continuance of 

 several species identical with those in the Lias which the sands 

 immediately superimpose, though the general style of the fossils 

 decidedly points to an Oolitic fauna, — and this the more so, the more 

 the oolitic structure of the rock prevails.- 



What, then, is here meant by the equivalents of the sand ? My 

 present opinion is, that the sands of Froeester are identical in time 

 with the mixed pisolitic beds of the Cheltenham district, and that 

 the iron-shot sands of the Dundry Hill and Somerset sections are also 

 of the same period : the pisolitic conditions prevailed in one part of 

 the Oolite sea, and sandy ones in another ; and hence the difference 

 of the fauna. 



At Haresfield Beacon is found a large Terebratula, at first named 

 T. lata, but now getting the name of a Lias shell, namely, T. punc- 

 tata, Sow. At Crickley Hill we have a variety of the same shell ; 

 but here the pisolitic stratum, as it occurs at Leckhampton, is some- 

 what changed, since we have as much as 60 feet of a sandy oolite in 

 blocks of hard stone, irregularly interpolated in beds of pisolitic cha- 

 racter. The most truly marked pisolite is near the top of this emi- 

 nently oolitic section, and it is here that the Ter. simplex and Ter. 

 plicata (Buck.) are in such abundance, together with large forms of 

 Ter. perovalis, which, however heterodox the notion may now seem, 

 I feel convinced will be ultimately considered specifically the same as 

 the Haresfield Hill form, and connected by the large specimens 

 thence obtained.* 



The following section of Crickley Hill may be compared with that 

 of Leckhampton : — 



ft. in. 

 5. Pisolite, with but a small admixture of oolitic 1 ^ ~ 



ragstone . . . . . . . . . . J 



4. Freestone, including pisolite . . . . . . 9 



3. Hard blocks of oolite, consisting in part ofl „- ^ 



very indurated pisolite . . . . . . J 



2. Sandy oolite, occasionally pisolitic . . . . 25 



1. Lias. 



Now here the sands are absent, but their thickness is made up 

 by siliceous and indurated oolites ; and where the true loose sandy 

 conditions prevailed, the difference is well marked by the fauna ; as 

 ever shifting sands and the want of calcareous matters were as 

 inimical to animals in the old as in the modern seas ; hence the 

 paucity of fossils in the true sandy deposits : but where muddy con- 

 ditions occasionally intervened for a while — as even in these sands, 



* This notion is not new, as Bronn (' Index Palseontologicus ') considers T. 

 perovalis as a synonym of T.lata, which, again, is the true T.ovoides(T. lata, Sow.). 

 D'Orbigny considers T. simplex to be a synonym of the same ('Prodrome'). Indeed, 

 these are among several forms of Terebratula from the same horizon, and yet pre- 

 senting as much difference as groups of our modern Mussel-shells. 



