104 REPORT—1840. 
rous slates and the overlying culm measures.” He particularly requested 
attention to the fact that the Petherwin slates and limestones, in the 
examination of them by Professor Phillips, as reported by Mr. De la 
Beche, had not been shown to contain one mountain lime species; and 
the utmost that Professor Sedgwick and Mr. Murchison, aided by the 
accurate discrimination of Mr. Sowerby, could elicit from them, was 
that “ one or two of them very nearly resembled mountain lime fossils.” 
Mr. Williams moreover stated that he had obtained the conclusive evi- 
dence of the fact that the Cornish killas overlaid the plant and culm 
rocks, which he contended annihilated at once the two hypotheses to 
which he objected, viz. the proposed identification of those rocks with 
the English coal-field, and the classification of the killas and Exmoor 
group as the old red sandstone. That the plant and culm rocks were 
subordinate to the killas, was shown not only by the fact of the former 
being brought up through the northern borders of the latter, in a great 
anticlinal line, but by observations made by Mr. Williams this summer, 
that nearly the whole of Dartmoor was invested by the lower culm 
measures, which everywhere dipped away from it below the killas and 
coral limestones. The proportion of carboniferous fossils from the South 
Devon slates and limestones, enumerated by Mr. Lonsdale in his late 
valuable memoir on that region, Mr. Williams contended did not justify 
the arranging those rocks, even in so close an approximation with the 
mountain limestone as the parallel of the old red sandstone. He also 
remarked on the total absence from the Devonshire strata of those 
numerous and characteristic species of fishes which had been found in 
the red sandstone so extensively in England and Scotland, and,.as Mr. 
Murchison’s recent researches had proved, even in Russia. 
Mr. Williams referred to a diagram and specimens of the hitherto 
considered “ granite veins,” from the bed of the Erme river, north of 
Ivy-bridge, which he referred to a tranquil fusion and conversion of 
the sedimentary rock, and not to injection. 
On a Pleistocene Tract in the Isle of Man, and the relations of its Fauna 
to that of the neighbouring Sea. By Epwarp Forses, F.L.S. 
Mr. Forbes stated that he did not appear as a geologist, but asa 
zoologist desirous of contributing to the progress of geology. In 
the course of his investigations with the dredge, he was frequently 
led to compare the present state of the sea with that of the land 
bordering it, and the results were such as mutually illustrated geo- 
logy and zoology. The northernmost part of the Isle of Man, left 
white in Mr. Greenough’s map, is composed of a great bed of pleisto- 
cene sand and marl, called by the people red marl, to distinguish it 
from the white marl, which fills up basins in the former, and in which 
the bones of the fossil elk are found. The red marl is marine, the white 
marl of fresh-water origin. The pleistocene tract so composed ex- 
tends from the slate mountains to the sea, terminating in high cliffs of 
sand and clay. The portion immediately bordering the mountains is 
ee 
