Slowly the calm sea ebbs. As the pulse of the great ocean beats, its glassy ribbon-waves flow swellingly along in long thin lines, and then drain rapidly away. Every now and then, with higher swelling motion, one wavelet ripples further in, leaving us doubtful for a moment of the tide's recess. But gently, surely are those slippery rocks unveiled, and on their smooth and purple flats the glittering fossils lie.

There, in their radiant iridescence in scores are pearly Ammonites. A. lautus, A. splendens, A. auritus, A. tuberculatus, and the little ribbed and everywhere bestrewn A. varicosus.

There hundreds of amber-like translucent Belemnites (B. Listen) protrude their spine-like forms from the dark blue solid clay.

Curled Hamites, small nut-shaped Nuculœ (N. pectinata and N. ovata), spiny Rostellariœ, Pterocera, and Naticæ, and black phosphatic caste of antique forms of crabs and prawns, and little stud- and cup-like corals await your gathering. Everything to your hand, resplendent as the sea has left them for you. Every here and there the smallest portion of some shell or crab reveals the untouched treasure buried underneath. Pick, trowel, knife, anything will dig into that moist yielding clay, or cut your treasure out. Patience and care are all you want.

As the season for active out of door geological work is now approaching, I propose to give a brief glance at some interesting features of the South Wales coal-field, in the hopes that pedestrian geologists may be tempted to make it one of the scenes of their labours. And they will be richly rewarded; for, though coal-fields generally give us an impression of a black, unsightly country, without vegetation or anything pleasant for the eye to rest upon, they are not all alike, and that of South Wales is as rich in beautiful scenery above ground, as it is in the precious mineral beneath. Glorious hills intersected by narrow valleys and wooded dells, each washed by its mountain-stream, and antiquities—in the shape of castles, abbeys, cromlechs, and cairns, may tempt the tourist to whom geology does not hold out sufficient inducement. It is in outward features, which I shall first touch upon, that this differs so much from other coal-fields, the basin being more clearly marked, and the underlying grits and limestones, being more uniform in their development than in any district in Great Britain.

This family, which has been termed Orthidœ by some authors, comprises several genera and subgenera, of which Strophomena, Streptorhynchus, and Orthis alone have been found represented in Scottish Carboniferous strata.

The genus Orthis forms a well characterized group, especially specifically numerous and abundant in the Silurian and Devonian systems, is considerably reduced during the Carboniferous period to appear no longer (P) in subsequent stages. Two species alone have been hitherto discovered in the Carboniferous rocks of Scotland.