CARBONIFEROUS BRACHIOPODA. 
267 
and shales of other localities in the Lanarkshire field. It occurs along with the former 
in the pit at Robroyston, and it is also found in the limestone which was worked at 
that place. ... It seems to have had a greater life-range through the strata than 
L. squamiformis, being found from our Lower Limestone up to the horizon of the slaty- 
band ironstone of Lanarkshire coal-field, which is 117 fathoms below Ell coal."^ 
4. LiNGULA, sp.? Sup., PI. XXX, fig. 9. 
In the black shale of the Millstone-grit series of Bishop Thornton, Uipley, Yorkshire, 
we find casts of a Lingula, which in external shape much resembles L. squamiformis. 
In size it measures about an inch in length by a little more than half an inch in breadth ; 
the sides subparallel, front nearly straight ; beak acutely acuminated ; but the chief pecu- 
liarity presented by these casts is that the shell must have been strongly concentrically 
striated, and the surface is marked by longitudinal striae or raised ridges of variable 
width. 
Genus Discina, Lamarck. 
5. Discina Craigii, Dav. Sup., PI. XXX, fig. 14. 
Discina Cbaigii, Dav. The Geological Mag., New Series, vol. iv, p. 17, pi. ii, 
figs. 1, 1 a, 187;. 
Upper or free valve very thin, and marginally nearly circular, about as broad as 
long, broadly rounded anteriorly, slightly less so posteriorly, conoidal, and of moderate 
elevation. Vertex submarginal; valves slightly flattened along the middle; surface 
marked by fine concentric, slightly raised, irregular lines of growth, with very fine 
radiating striae, seen more or less distinctly here and there over its shining and highly 
polished surface. Lower or pedicle valve not known. 
^ Mr. James Kirkby writes me: — "For the past three years I have paid most attention to the 
Calciferous Sandstone series, which forms the lowest local division on the east side of Scotland. The 
junction of these rocks with the Devonian formation is seen on the Fife coast ; but I have got a careful 
section made of nearly 4000 feet of strata below the base of the Carboniferous series. Low down in this 
mass of strata highly fossiliferous bands of limestone come in. Certain species of Lamellibranchs are very 
rife, but the only Brachiopods that have occurred to me are Lingula mytiloides and Rhynchonella 
pleurodon ; these are the oldest Carboniferous Brachiopods that I have met with. A thousand feet higher 
up, or about 7 feet below the base of the Carboniferous Limestone, Productus semireticulatus, Athyris 
ambigua, Spiriferina cristata, and Discina nitida appear, with other shells and corals, and still higher up 
towards the upper portion of the series a few other species occur. 
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