Geology and Physical Geography. 369 



Dura Den is situated in the upper part of the Old Red 

 Sandstone, which is now interesting in a paleontological view, 

 on account of the fossil fishes with which it abounds. Dr 

 Anderson laid before the meeting a beautiful collection of 

 these fossils, and stated it as his opinion, that among the 

 specimens exhibited, there were several species, and even 

 genera new to paleontologists. The accuracy of this opinion 

 was questioned by some of the members of the Association, 

 but minute examination we understand was not gone into 

 for want of time. 



Professor Sedgwick then described the Palaeozoic Rocks of 

 the south of Scotland. After referring to the formations 

 which surrounded them, and to the deposits which occupy a 

 hif^her geological position, the Rev. Professor said he had 

 endeavoured to ascertain the axis of the great mountain 

 chain which traversed the south of Scotland. He believed 

 that the axis was at the centre — that was to say, that newer 

 rocks were to be found on the north and south sides of it. 

 He then went on to say, that in this great mountain chain 

 beds exist which are nearly equivalent to the Caradoc sand- 

 stone of the Chairman (Sir R. Murchison), and also to the 

 Conniston limestone of the high part of Lancashire, where it 

 adjoins Cumberland. These beds were marked by the fossils 

 which characterized the Silurian of his friend the Chairman. 

 Such deposits occurred at Girvan, Colmonell, in Ayrshire, 

 and in some parts of Wigton shire, and at Balmea, in Kirk- 

 cudbright. Below these beds Graptolites are found, and 

 these Graptolites are of such a nature as to connect them 

 with the black slates of New York, in which fossils of a 

 similar nature occur. He had figured in a work, which would 

 appear before long, thirteen different species found here, 

 which were described only in American works. In Scotland 

 these Graptolites are most abundant about Moffat — the so- 

 called alum slate being full of them. This portion of the 

 palaeozoic formation the learned Professor conceived to be 

 much below any beds which have hitherto afforded fossils, 

 and he believed that his friend (the Chairman's) system would 

 have to undergo some change before the palaeozoic rocks of 

 the south of Scotland could find a place in that arrangement. 



VOL. XLIX. NO. XCVIII.— OCTOBER 1850. 2 A 



