290 GILLIGAN : THE LOWER PER:\IIAX AT ASHFIELD, ETC. 
38-58 per cen.1. in bed J, which is immediately below the massive 
Magnesian limestone. 
These beds correspond, of course, in position with the Marl Slates 
of Durham, but have not yielded the fish fauna of those beds. 
Petrology of the Conglomerate and Associated Sands. 
Among the pebbles the following have been noted : — sandstone, 
quartz, clay ironstone, hematite, chert and pink felspar. The material 
is not at all well compacted, but layers occur sufficiently indurated to 
yield sections for the microscope, and several have been made and 
examined with the following results. 
The grains of hard material are all exceedingly well rounded, 
while the softer materials are somewhat flattened. The dominant 
constituent is quartz, the grains of which are chiefly of the complex 
type. Some of them show an extreme degree of mylonitisation, while 
others have " crenulate " and "mortar structure" well developed. 
Many grains of sandstone are present which are evidently from the 
under-lying rock. Chert-grains are numerous, but show no traces ot 
organisms. Limonite and hematite are also common. 
Felspar, other than microcline, is rather rare in the fresh condition, 
while muscovite is present in somewhat large flakes. A few pieces of 
micro-pegmatite have been noted, having in two cases lath -shaped 
felspars associated with and penetrating the grain. The matrix is 
chiefly calcite. 
Heavy Minerals in the Sands. 
These were separated by means of a SoUas bottle and Theukt's 
Solution : — 
Cubic. — Garnet, Magnetite, Fluorspar. 
Tetragonal. — Zircon, Rutile, Anatase, Xenotime. 
Rhombohedral. — Ilmenite, Hematite, Limonite, Tourmaline, Apa- 
tite. 
Orthorhombic. — Staurolite . 
Monoclinic. — Biotite, Chlorite, Epidote, Monazite. 
Triclinic. — None . 
