OF THE CABBONIFEROUS STBATA. 



196 



sort of spiral organization, by no means unlike that of the 

 planorbis or spirorbis, to which they were referred by an 

 eminent conchologist, whose opinion regarding them I have 

 consulted. But on renewed examination of these remains, 

 which, owing to an infiltration of calcareous matter, have had 

 their forms tolerably well preserved, I am now inclined to place 

 some doubt upon the judgment which had been passed upon 

 their character. The external form of one animal most resem- 

 bles that of the nautilus, but we are totally precluded from 

 identifying it with that class of mollusca, as the internal con- 

 stitution of its shell shews no septa whatever, but on the 

 contrary, approaches to that of the planorbis. It may, per- 

 haps, be considered as a new genus altogether — referable to 

 mollusca" 



Mr. Morris, F.G.S., in his excellent Catalogue of British 

 Fossils, also classes it amongst mollusca. 



Professor Goldfuss* considers the microconchus an annelid, 

 like the spirorbis, and describes it as S. omphaloides. Col. 

 Portlock, in his Memoir of the Geological Survey of Ireland, 

 describes it under the same name. Sir Charles Lyell, in the 

 last edition of his Manual of Geology, at p. 324-5, still calls 

 the fossil microconchus carbonarius ; but describes it as " the 

 microscopic shell of an annelid of an extinct genus allied to 

 serpula or spirorbis." 



From the above quotations it is pretty evident that consi- 

 derable doubt has existed as to whether or not the microcon- 

 chus should be classed with mollusca or annelata. 



In the Lancashire coal field this fossil is found from the 

 lowest up to the highest strata — generally in black bass. 

 In the roof of Mr. Stock's coal at Shaly Brow near Bil- 

 linge, it constitutes a bed of about six inches in thickness, 

 and is mingled with the remains of fishes. In the thick bed 

 of large shells lying about fifty yards above the Arley Mine» 



* Howse, T. N. I. C^ vol. i. p. 259. 1848. 



