MITCHELL ON THE FLAGSTONES OF FORFARSHIRE. 



147 



have made already, though not nearly sufficient to clear up many 

 highly important questions, are still sufficient to give very great 

 encouragement ; and I therefore feel anxious to induce others to turn 

 their attention to this branch of research, being convinced that it 

 cannot but yield a bountiful harvest of facts, when studied with 

 perseverance and zeal. 



ON THE FLAGSTONES OF FORFARSHIRE. 

 By Hugh Mitchell, of Craig. 



There is a close resemblance between the fossil contents of the 

 " Upper Ludlow Tilestones," as described by Mr. Roberts, of Kidder- 

 minster, in the last number of The Geologist, and those of certain 

 strata developed in this neighbourhood. The rocks of the southern 

 districts of Forfarshire have been described by Fleming and Miller, 

 and their fossils have attracted the attention of the scientific world. 

 I am acquainted with sections in the north-eastern division, an account 

 of which has not yet appeared in print, and it may be of interest to 

 indicate their organisms. 



Among our fish-remains I have twice met with heads of the Cephal- 

 as2ns Lyellii ; but the fossil is more common in other localities. The 

 Pteraspides, wliich seem to be so frequent in the English beds, I do 

 not knowj unless some of the fragmentary remains, like pieces of skin 

 or shell, and to which I shall hereafter refer, belong to the genus. 

 From one of our sections I have collected several specimens of at least 

 two species of fishes, entire and beautifully preserved. They are small 

 creatures, and have all their fins armed with spines. One of my 

 specimens is a very tiny fish, scarce an inch in length, but with its 

 every spine in its place, and, so far as regards its dermal covering, a 

 complete picture. We have also a considerable variety of Ichthyo- 

 dorulites. Some of them resemble the Onchus-spines figured in the 

 first edition of Sir Roderick Murchison's " Siluria." Others are larger 

 and have more the appearance of true fish-defences. Mostly all our 

 fossils are mere impressions in the stone ; but the bony matter of the 



