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A part was compact and blue, very crystalline, and full of encrinitic fossils, and probably nummulites, but all were too much altered for determination. This, from its mineral characters, appears to be the same limestone formation which occurs throughout the Himalaya and Western Tibet; but the fossils I collected are in too imperfect a state to warrant any conclusions on this subject.
Separate groups of strata are often characterised by distinct species of nummulite; thus the beds between the lower Miocene and the lower Eocene may be divided into three sections, distinguished by three different species of nummulites, N. variolaria in the upper, N. laevigata in the middle, and N. planulata in the lower beds.
The lower part of the calcaire grossier, which often contains much green earth, is characterised at Auvers, near Pontoise, to the north of Paris, and still more in the environs of Compiegne, by the abundance of nummulites, consisting chiefly of N. laevigata, N. scabra, and N. Lamarcki, which constitute a large proportion of some of the stony strata, though these same foraminifera are wanting in beds of similar age in the immediate environs of Paris.
When the geologist looks to-day for the floor of the Eocene ocean, which he recognises by the shells of the Nummulites, he finds it 10,000 feet above the sea-level in the Alps, 16,000 feet above the sea-level in the Himalaya, and 20,000 feet above the sea-level in Thibet.
A similar fortune was experienced by the ferns and club-mosses which formed whole forests in the carboniferous period. Other groups which once played a great rôle, are now wholly extinct; for instance, the trilobites of the primary, the sauria of the secondary, the nummulites of the tertiary periods.
Heer has mentioned several species which are common to this Alum Bay flora and that of Monte Bolca, near Verona, so celebrated for its fossil fish, and where the strata contain nummulites and other Middle Eocene fossils.
External surface of one of the nummulites, of which longitudinal sections are seen in the limestone. b. Dr. T. Thompson found nummulites at an elevation of no less than 16,500 feet above the level of the sea, in Western Thibet. The same is also very common in rocks of the same age in the Carpathians.
According to M. Hebert, the most characteristic Barton Clay fossils correspond to those of the Gres de Beauchamp, or Sables Moyens, of the Paris Basin, but it also contains many common to the older Calcaire Grossier. Voluta athleta, Sol. Terebellum fusiforme, Lam. Cardita sulcata, Brand. Crassatella sulcata, Sowerby. Nummulites variolaria, Lam. Var. of Nummulites radiata, Sowerby.
The Nummulites planulata is very abundant, and the most characteristic shell is the Nerita conoidea, Lam., a fossil which has a very wide geographical range; for, as M. d'Archiac remarks, it accompanies the nummulitic formation from Europe to India, having been found in Cutch, near the mouths of the Indus, associated with Nummulites scabra.
All the mountain-chains, such as the Alps, Pyrenees, Carpathians, and Himalayas, into the composition of whose central and loftiest parts the nummulitic strata enter bodily, could have had no existence till after the Middle Eocene period. During that period the sea prevailed where these chains now rise, for nummulites and their accompanying testacea were unquestionably inhabitants of salt water.
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