BUFFALO SOCIETY OF NATURAL SCIENCES 139 



show. Even in the Pentland Hills the base of the Wenlock is no- 

 where visible, the beds standing on end for the most part and stick- 

 ing up through the Old Red Sandstone. In Lanarkshire, however, 

 there occurs in the Lesmaghagow inlier only, below the Ludlow, a 

 series of blue greywackes with shale, partings which is 1300 feet 

 thick and has proved unf ossiliferous throughout except in one locality 

 where a few specimens of Murchisonia (specifically undeterminable) 

 and some doubtful forms called Orthis have been found. It has been 

 thought by the Scottish Survey that part at least of this formation 

 was Wenlock in age. I should like to offer the following purely theo- 

 retical suggestion. It has been shown that during Tarannon time 

 rivers flowing from the Eastern Highlands carried down pebbles and 

 boulders which were deposited in the Central Belt. Probably the 

 whole of central and northern Scotland was above water then, and 

 either subaerial erosion or deposition was going on. The 1300 feet 

 of greywackes and shales below the Ludlow in Lanarkshire might 

 represent in their lower part delta or torrential deposits accumu- 

 lated during Tarannon time and in their later part similar deposits 

 during Wenlock time. Their unfossiliferous character and great 

 thickness would thus be accounted for. Future study in those rocks 

 should be directed towards the search for cross-bedding, if any, and 

 the type represented, for plant remains, tracks, and eurypterids. As 

 the Wenlock sea advanced northwards — there is little reason to doubt 

 that it did, for the same marine fossils are found in the Southern Belt 

 and in the Pentland Hills — it reworked the Tarannon, and a basal 

 sandstone, conglomerate or shale was formed, depending upon the 

 nature of the Tarannon continent where the sea transgressed. Thus 

 along the northern border of the Southern Belt the basal Wenlock 

 consists of "greenish grey, flaggy grits, separated by grey shale bands, 

 some of which are crowded with Crossopodia, Nemertites, and other 

 tracks, resembling those found in the Hawick Rocks." On the Slitrig 

 Water the shales and surfaces of the greywackes are crowded with 

 tracks. These rocks pass conformably downwards into the Tarannon 

 rocks of Hawick, indicating that the actual seashore at the close of 

 Tarannon and beginning of Wenlock time must have been just about 

 in this region. The unfossiliferous grits and greywackes (the first 

 division of the Wenlock) appear along the northern border, while 

 the second division occupies all of the rest of the belt to the south 

 except for small patches or inliers in the extreme south where the 

 third division of the Wenlock is seen; there are also inliers in various 



