410 Sir Roderick I. MurchisonU 



" In Herefordshire and Shropshire the passage of the upper 

 members of the Silurian rocks into the inferior strata of the Old 

 Red group has been well shown by Mr. Lightbody, and the fossils 

 of its lower members have been vigorously collected, while in 

 Scotland Mr. Geikie and others have shown the upward passage 

 of its superior strata into the base of the Carboniferous rocks, and 

 Dr. Anderson announces the finding of shells with Crustacea in 

 the lower or gray beds, south of the Tay. I may here note that 

 the point which I have been for some years endeavouring to es- 

 tablish as to the true position of the Caithness flags with their 

 numerous ichthyolites seems to be admitted by my contempor- 

 aries. The lamented Hugh Miller considered these ichthyolites 

 as belonging to the lower member of the group, and had good 

 grounds for his views, since at his native place, Cromarty, these 

 fish beds appear very near the base. But, by following them into 

 Caithness and the Orkneys, I have shown that they occupy a 

 middle position, while the true base of the group is the equivalent 

 of the zone with Cephalaspis, Pteraspis, and Pterygotus. 



" And here it is right to state that the Upper Silurian rocks, 

 which are clearly represented in Edinburghshire, and which in 

 Lanarkshire seem to graduate upwards into the Lower Old Red or 

 Cephalaspis sandstone, are wanting in the Highlands, thus ac- 

 counting for the great break which there occurs between the 

 crystallized rocks of lower Silurian age and the bottom beds of the 

 Old Red Sandstone. 



" Ofthe Old Red Sandstone of Scotland and Herefordshire I may 

 be permitted further to observe that its downward passage into 

 the uppermost Silurian rock and the upward passage of its higher 

 strata into the Carboniferous strata has been well developed ; the 

 one near Ludlow, chiefly through the labours of Mr. Lightbody ; 

 the other in Scotland, through the researches of the Government 

 geologists Howell and Geikie, as well as by those of Mr. D. Page 

 and other observers. On this head I may however note what 

 my contemporaries seem now to admit, that the removal of the 

 Caithness flags and their numerous included ichthyolites from the 

 bottom of this group, and their translation to the central part of 

 the system, as first proposed by myself, is correct. In truth, the 

 lower member of this system is now unequivocally proved to be 

 the band with Cephalaspis, Pteraspis, &c., as seen in Scotland, 

 England, and Russia. The great break which has been traced in 



