The student of fossil botany encounters greater difficulties in his efforts to restore the vegetation of former epochs in the earth's history, than those which beset the labours of the comparative anatomist in his restoration of extinct animals. These difficulties arise chiefly from two causes: First, the absence in the vegetable kingdom of a substance which would resist decay like the solid skeleton found in all the vertebrate, and in many of the invertebrate members of the animal kingdom, causes the fragments of plants which have escaped decomposition to be preserved much less perfectly than the remains of animals. Carbonaceous stains or amorphous casts are the most frequent indications of the former vegetation of the globe; specimens exhibiting structure are comparatively rare; and it is such specimens only that give certain evidence of the nature and affinities of the organisms to which they belong.

In the June Number (p 251), we gave Messrs. Pictet and Lory's most recent views on the disputed age of those beds which contain the Terebratula diphya or T. viator of Pictet. In order to complete thier views I now publish a letter recently received from M.Héberts, which he requests me to add to the present notes.

For many years the various Coal-shales and other strata associated with the Coal-seams of Northumberland have been known to be rich in the remains of Plants, and the majority of the specimens which are illustrated in Lindley and Hutton's elaborate work on the Flora of the Coal-period were obtained from collieries in Northumberland and the adjoining county, Durham. It is only within the last few years that close attention has been directed to the investigation of the fauna of the Northumberland coal-fields. The first systematic investigator of the fauna of the Carboniferous period in this locality was Mr. Thomas Atthey, late of Cramlington, now of Gosforth; and within the last few years Messrs. Kirby, Sim, Taylor, and Craggs have each secured good collections of the Carboniferous fossils.

Having had our attention directed by Mr. Barkas's paper to the specimens of this genus in the National Collection, and compared Mr. Barkas's figures with Mr. T. Atthey's description of Ctenodus tuberculatus [see “Annals and Magazine of Natural History” (4th series), Feb. 1868 (p. 83)]; Mr. W. Davies having also kindly pointed out to us a small but very perfect palatal tooth (see Plate IX. Fig. 3), probably from the Coal-measures of Carluke (from the collection of the late Mr. Alexander Bryson of Edinburgh), closely agreeing with Mr. Atthey's description in all its characters; we have thought it well deserving of a place in our Plate.

The district to which attention is directed is situated in the centre and the most elevated part of Great Britain, which is thickly inhabited by an industrial population, many of whom are occupied in the working of Lead-mines. The Agent's house of the Beaumont Mines is at an elevation of 1400 feet above the sea, Kilhope Law rises 2206, while Crossfell (capped by Millstone Grit) attains a height of 2901 feet; Dufton Pike 1575 feet, and the Cheviots 2676 feet, the three counties of Northumberland, Cumberland, and Durham meeting at Rampgill Head; Durham, Yorkshire, and Westmoreland at Cauldron Snout. This elevated district, bounded on the east by the Tyne and Wear Coal-field, and on the west by the Whitehaven field, chiefly consists of the Carboniferous rocks, and presents varied physical features. The Penine chain, of which Crossfell is a part, extends from the borders of Scotland to Derbyshire, and from its westerly trend it forms the watershed, whence on the east side fall the waters of the Tyne, Wear, and the Tees. The country presents a varied aspect; to the east are broad low plains, succeeded by rolling hills and dreary elevated moors, followed by a more hilly and more rugged district, rising gradually on the east side of the Penine chain, and descending more steeply on the western side. These, together with the character of the rocks, influence the vegetation of the country, as shown by the “basset” of the Great Limestone, which forms almost the boundary of cultivated land and human habitations. Above it (as Mr. Sopwith observes) are more or less brown and dreary moors, and below it the hill-sides present a green surface and flowery meadows. The counties of Northumberland and Durham occupy about 2905 square miles, three quarters of which belong to the Carboniferous strata.