128 SILURIA. [Chap. VII. 
cited Pentamerus galeatus, Strophomena depressa and S. euglypha, Leptaena 
laevigata, Atrypa reticularis, and Rhynchonella "Wilsoni. Scarcely any Brachio- 
pod is strictly peculiar to it, unless it be the small but characteristic Lingula 
lata, PI. XX. f. 6. In this view, the Lower Ludlow shale might be classed with 
the Wenlock formation ; but the other forms of Mollusks, above noticed, give to 
it a distinct character, and entitle it to rank locally as a separate subformation. 
Aymestry or Ludlow Limestone*. — The want of persistence over wide 
areas of any mass of solid limestone in the centre of the Ludlow formation 
has been adverted to. In some parts of South Wales, where the calcareous 
matter is absent, it is difficult to trace even the place of this band in the 
Ludlow rocks ; but in Herefordshire and Shropshire, and again at Sedgeley 
in Staffordshire (near Dudley), it is a dark-grey limestone, worked rather 
extensively for use. Even where the lime is sparingly distributed, the 
rock is a highly calcareous flagstone, and may generally be recognized by 
its well-defined joints and predominant fossils. 
This central member of the Ludlow formation was named by me after 
the beautiful village of Aymestry, where the rock is well laid open, and 
its relative position as well as fossil contents were elaborately worked out 
by my friend the late Rev. T. T. Lewis f. The clear distinction of this 
rock from the "Wenlock Limestone was, indeed, first made by him ; so that, 
Whiteway Head. An escarpment of Aymestry Limestone. Strata dipping to the S.E. 
(From Sil. Syst. p. 243. Sketched by the late Eev. W. E. Evans.) 
* In a communication to the Geological Society though still colouring the thick calcareous beds as 
in 1863, Mr. Lightbody stated, after observations before." Now, as in my original classification it 
by himself and Mr. Marston, that, in portions of was specially explained, and repeated in editions 
the Ludlow promontory which are much dislocated of 'Siluria,' that the term Aymestry or Ludlow 
(Mocktree Forest), certain beds hitherto included Limestone had reference only to limited tracts of 
in the Upper Ludlow rocks ought to be, from their England, and was inapplicable to other wide tracts, 
fossils, classed rather with the Aymestry Lime- whether at home or abroad, where the Ludlow- 
stone. Again, indicating that this limestone is Eock formation has no such subordinate band, it 
more naturally connected with the lower rock, he seems to me that Mr. Lightbody's view is quite in 
asks " if it would not be better to discontinue the unison with my own. See Quart. Journ. Geol. 
name Aymestry Limestone as a division alto- Soc. vol. xix. p. 369. 
£ ether, and to call all the beds between the Upper t See Sil. Syst. p. 201. 
udlow and the Wenlock simply Lower Ludlow, 
