1863.] LIGHTBODY AYMESTRY LIMESTONE. 371 



Strophomena depressa, S. filosa, and Atrypa reticularis, all abun- 

 dantly; Acrocidia Haliotis, Lingula striata, Proetus Stokesii, Encri- 

 nurus punctatus, E. variolaris, and Lichas BucMandi. Besides 

 these fossils, however, the character of the rock, if closely examined, 

 testifies to the same effect, as it is much more calcareous than the 

 true Upper Ludlow beds ever are, and shows the honeycombed 

 structure in the joints along the bedding. This is shown also by the 

 whiteness left, on the central parts of the cliff, by the trickling of 

 water, which has given it the name of White Cliff. 



The consequence of this oversight has been that the admixture of 

 Aymestry Limestone fossils (most of which run through the Lower 

 Ludlow) with the Upper Ludlow list has rendered it impossible, 

 where the thick calcareous beds do not intervene (as is the case 

 towards the west), to discriminate between the Upper Ludlow and 

 the Lower Ludlow, and they are consequently coloured the same on 

 the maps. 



When we consider that all through the strata, from the top of 

 the Aymestry Limestone, there is a constant intercalation of cal- 

 careous beds, to the bottom of the Lower Ludlow, of which the 

 Aymestry Limestone is only an exaggeration arising from the casual 

 occurrence of large beds of shells or corals in certain places, — if we 

 further consider the identity of a large proportion of the fossils of 

 the Aymestry Limestone with those of the Lower Ludlow, parti- 

 cularly when we find such local fossils as the Lower Ludlow Star- 

 fish in beds above the whole thickness of the Aymestry workable 

 limestone, — if we consider the impossibility of fixing upon the point 

 where the one formation ends and the other begins, — and, lastly, 

 that the Aymestry or thick limestone does not exist through large 

 tracts of Ludlow rocks, but only where certain fossils are very abun- 

 dant, — would it not seem better to discontinue the name Aymestry 

 Limestone as a division altogether, and to call all the beds between 

 the Upper Ludlow and the Wenlock simply Lower Ludlow, though 

 still colouring the thick calcareous beds as before ? 



