84 



ORGANIC REMAINS OF THE FRESHWATER LIMESTONE. 



of this rock, I was struck with its strong resemblance to certain " lacustrine" lime- 

 stones of France and Germany, which by their imbedded organic remains are known 

 to have been formed under fresh water; and when I further discovered in 1832, that 

 nearly all the fossil remains in the limestone or the associated strata, might be referred 

 to terrestrial and fluviatile origin, one only being doubtful, I named it a "freshwater 

 limestone." (See Geol. Proceedings, Phil. Mag., N.S. vol. iii. p. 225.) I traced this cal- 

 careous band at intervals from Nobold, near Shrewsbury, to Asterley beyond Pontesbury, 

 always occupying the same place between the first and second coals, and varying very 

 slightly in mineral characters. At Westbury it thins out, but at Braggington, near the 

 western termination of the field, it reappears in a bed of about three feet thick. The 

 characteristic fossil of the limestone is a very minute discoid univalve, resembling on 

 first inspection Planorbis Nautilus, Fleming, and with this is associated a small bivalve 

 having the form of a Cyclas, and also a small Cypris. In addition to the above-named 

 fossils, the remains of fishes have been discovered, the most remarkable of which 

 is a new species of the genus Ctenodus of Agassiz, named by that author Ctenodus 

 Murchisonii 1 . Another fragment of a fish subsequently found in the shale above the 

 limestone by Professor Phillips, proves to belong to Meg alichthys Hibberti. I here insert 

 a wood-cut illustrating the unpublished shells which are most characteristic of this 

 limestone in Shropshire. 



A. 1. B. D. 1. D. 2. D. 3. D. 4. D. 5. D. 6. D. 7. 11- 



A. 2. A. 3. C. D. 8. D. 10. D. 9. 



A. Cypris inflata. A. T. A. 2. and A. 3. are magnified about twelve times. 



This Cypris is obovate, smooth, and very much inflated : in the latter character it differs especially from all other known 

 fossil species. 



B. Two representations of a transversely elongated, rather compressed shell, resembling a Cyclas : one of them is magnified. 



C. A shell resembling Modiola from Ardwick near Manchester. This shell has not been observed in Shropshire. 



D. Microconchus carhonarius. It is thus named until its characters are better understood; it does not appear to be chambered. 

 D. 2. to D. 7. are slightly magnified figures. D. 8. and D. 9. are highly magnified; over each of these, and at D. 1. are 

 representations of the natural size. D. 10. refers to two figures of the striated surface. D. 8. at * * shows the impres- 

 sion of the substance to which the shell has been attached. See further description by Professor Phillips, p. 88. In ex- 

 amining this shell Mr. Lonsdale perceived that it was probably the same as the minute shell figured among Martin's 

 Petrificata Derbiensia as Conchy liolithiis Helicites (pusillus, pi. 25.), and which is stated to be of rare occurrence in coal 

 shale at Chesterfield. 



1 The fossil fish named Ctenodus Murchisonii by M. Agassiz was presented to me by the very Rev. Arch- 

 deacon Waties Corbett : a figure of this fossil may be seen in the Zoological Journal, vol. i. PI. 8. p. 252. 



