182 Proceedings of the Royal Society of Edinburgh. [Sess. 
the lower division, and sandstones in the upper. The outcrop o£ massive 
encrinital limestone which is seen in the Levern Water just below the 
Cross Arthurlie Street Bridge, Barrhead, is regarded as the Main Hosie 
Limestone.* We shall see that this forms a well-marked fossiliferous 
horizon all over Central Scotland. 
The next calcareous horizon in ascending order is the Top Hosie Lime- 
stone, sometimes known as the Calderwood Cement, because of its typical 
development in that district. Between it and the underlying Main Hosie 
comes the Lillies Coal and Oil Shale. The Top Hosie is nowhere exposed in 
the Hurlet district at the surface, but it has been found in the ironstone 
pits sunk by Messrs Baird at Corkerhill. It is a dark calmy limestone 
with strings of small gasteropods and brachiopods well preserved. The 
distinctive feature of this horizon is the presence above and below the 
limestone of shales crowded with Posidonomya corrugata , with which is 
associated a very characteristic faunal group. 
The Top Marine horizon of the Lower Limestone Series is represented 
in the West of Scotland by a highly fossiliferous blaes, the upper part full 
of Lingula , the lower rich in small Producti. It is nowhere exposed at the 
surface in the Hurlet district, but was found in the pit at Corkerhill just 
referred to. It has also been long known to occur in the pits at Inkerman, 
where the calcareous shale passes into a limestone. To the north of 
Glasgow, in the Campsie district, this horizon is represented by a bed of 
limestone containing small brachiopods associated with Ceriopora inter- 
porosa. The limestones on this horizon are abundantly charged with the 
marine alga Spirophyton cauda-galli, which also occurs in great quantities 
in the associated sandstones. 
Such, then, is a summary of the Hurlet type section, giving the principal 
characteristics of the limestone horizons from the Hollybush Limestone at 
the base to the Top Marine Band. It has been shown that there is un- 
fortunately a great paucity of exposures in the district, and but few con- 
tinuous sections of any length. For the purpose of strengthening and 
widening our conception of the Hurlet Sequence in Renfrewshire we 
briefly describe certain other sections. 
An important section showing an almost continuous sequence from the 
Hollybush Limestone up to the Hurlet Limestone is exposed at Nether- 
craigs, miles to the west of Hurlet. At this locality the strata have 
been thrown into a small basin, which is faulted against the volcanic rocks. 
The outcrops of the Hollybush, Blackbyre, and Hurlet Limestones appear 
in three more or less continuous rings, with the last-mentioned limestone 
* Trans. Geol. Soc. Glasgow , vol. xv, p. 210. 
