Retrospective Criticism, 475 



In p. 128,, at the end of Mr. Conway's first communication 

 on this interesting subject, we remarked that " An able geo- 

 logist earnestly advised us to procure a specimen of the 

 ' limestone/ " as he was desirous to satisfy himself, by actual 

 inspection, whether the rock in which the crinoideal re- 

 mains had been found were truly limestone. To our appli- 

 cation for specimens Mr. Conway obligingly answered by a 

 prompt and liberal supply. Specimens have been submitted 

 to our friend, the geologist spoken of, who has subsequently 

 reported on them as follows. — Cond. 



Sir, In reply to your enquiry respecting the limestone 

 you sent me a specimen of, in which the supposed lily encrinite 

 was found by Mr. Conway, I have no hesitation in stating 

 that it is identical with many of the beds of nearly black moun- 

 tain limestone in North Wales, Yorkshire, and Westmoreland; 

 it contains the characteristic fossil of mountain limestone, the 

 Productus. The well-known black madrepore limestone, as it 

 is commonly called, is represented by black chert in one 

 of the specimens, but the embedded madrepore preserves its 

 calcareous character. Mountain limestone is very extensively 

 spread over the inland counties in Ireland ; but in that country 

 it chiefly occupies comparatively low ground, in what has been 

 called ike great limestone valley of Ireland, In England and 

 Wales it forms mountains of great elevation and magnitude. 

 In one of the specimens of Irish limestone there are several 

 disjointed articulations of a stem of what, I suppose, Mr. Con- 

 way considered the lily encrinite; the articulations do not 

 form circular discs, as in the stem of the lily encrinite, but are 

 angular, having either five or six sides ; as they are partly em- 

 bedded, it is difficult to determine which : they are not stellular, 

 like the discs of the pentacrinite. It is not easy to discover, 

 from the drawing of Mr. Conway, in p. 126.., whether the 

 stem is rounded or angular. The muschelkalk in which the 

 lily encrinite is found in the eastern departments of France, 

 and in Germany, bears a much nearer relation to lias lime- 

 stone, both in its mineral and zoological characters, than to 

 mountain limestone. Its geological position is below the 

 upper red marl and sandstone, which separates it from lias : 

 its thickness, in some parts, is more than 600ft. The muschel- 

 kalk has not hitherto been found in Great Britain or Ireland. 

 I have not seen any specimens of the lily encrinite in which 

 the arms were not completely folded ; but, as this could not be 

 their common position when the animal was living, they must, 

 in their unfolded state, have resembled, in general appearance 

 the encrinite of which Mr. Conway has, in p. 126., given the 

 drawing. Yours, &c. — JR. B. August, 1833. 



