Horizon of Dr. Scolder's Ditliyrocaris. 275 



one time exposed at this point is made clear both by the Survey 

 map and by Mr. Blair's paper published in our Transactions (1889, 

 p. 133). In this paper Mr. Blair describes it as exhibiting " a wider 

 variety and more abundant quantity of delicate organisms than I have 

 yet seen in any of these deposits". 



The section between the railway bridge and the signal box at the 

 Paisley end of the cutting is now so completely grassed over that not 

 a vestige of rock can now be seen, and we are left to judge by analogy 

 with the general sequence of the district what the horizon of the 

 limestone formerly exposed at this point may be. Fortunately, 

 though exposures are extremely rare upon this horizon in this 

 district, yet the cumulative evidence is such as to leave no room for 

 any doubt in our minds that the limestone formerly exposed at this 

 point, known locally as the Gallowhill Limestone, must be the 

 equivalent of the Blackbyre Limestone of the Hurlet type section. 

 On the east side of the railway bridge the lowest bed seen in the 

 railway cutting is a band of grey cement limestone with rootlets, 

 which all over this area is a well-marked horizon lying immediately 

 below the Hurlet Coal and above the Blackbyre Limestone. It can 

 be seen at Crookston Farm cropping from below the dolerite sill in 

 exactly the same fashion as it does in this cutting, but there in 

 addition to the rootlets it contains fish teeth, Spirorbis, and 

 entomostraca. 



Below this rooty cementstone there comes in the Hurlet district 

 a variable thickness of shales succeeded by tlie Blackbyre Limestone. 

 This view has been expressed in the section in Pig. 2 ; a is the 

 Gallowhill Limestone, being the top of the Blackbyre Limestone, 

 shown as folded into a gentle arch, which gives off in its eastern 

 limb, b the cement limestone with rootlets, c thin bands of lime- 

 stone with entomostraca and fish remains, d beds of shale and 

 fireclay, e intrusive sill of dolerite, f and g Hurlet Coal and alum 

 shale, and h Hurlet Limestone. 



As has already been stated, no exposures of the Gallowhill Lime- 

 stone can now be seen at any of the localities where it Avas formerly 

 worked. But the position of two of the quarries south of the 

 Arkleston Print Works can still be seen. Another quarry appears to 

 have been opened a little to the south of Gallowhill, opposite the 

 Mote Hill. The positions of these quarries are indicated on the map, 

 and they seem to have been somewhat extensively worked about the 

 year 1835, when Scouler's fossils were found, the old Powder 

 Magazine between Arkleston and South Arkleston having been built 

 of it, as well as a large number of the dykes in the Gallowhill 

 Policies. It was also used in some walls in the neighbourhood of the 

 Paisley Barracks, where it can still be seen. This may have some- 

 thing to do with Armstrong's statement that Scouler's fossils were 

 found in a limestone excavated for the foundations of the Paisley 

 Barracks. 1 That the Gallowhill Limestone must extend considerably 



1 Since writing this paper I have been informed by Mr. E. Houston that in 

 making the foundations for the villas adjoining the Paisley Barracks it was 

 found that slabs of the Gallowhill Limestone had been used to fill up old 

 hollows in the surface of the ground. 



