ESTHERIA MIDDENDORFII. 113 



cipitous bed in the shale. At the depth of about a fathom from the surface the fossils 

 are found in this shale. The Eish and Shells^ occur throughout, and near one another, and 

 not at all in separate beds ; yet on the bank-cliff itself Shells occurred, but further inland 

 Fish were laid bare by digging. The Crustaceans {Limnadid) are found, however, in 

 another place of the said bank, evidently an ancient puddle of standing water. The shale 

 s as yet not otherwise penetrated, but evidently extends to a great depth. The upper- 

 most beds are, as it were, fatty, perhaps from the remains of decomposed Fish. About 

 40 versts southward from this place begin the wide, endless plains of the Mongohan 

 Steppes. On the right bank of the Onon, at 30 versts upwards from the mouth of 

 the Turga, Fish-casts are also said to occur ; according to the report of the Bm-ats, there 

 the shale is, as it were, pervaded with mica-flakes. " 



M. E. d'Eichwald, of St. Petersbm-g, has favoured me with some pieces of this Sibe- 

 rian shale ; he speaks of it as coming from near the village Tourtscha, on the banks of 

 the Bibaya stream, which falls into the River Belaya, in the district of Nertschinsk. 



Several specimens of this grey shale, containing Fishes and the interesting Entomos- 

 tracans under notice, were presented to the Museum of the Geological Society in 1858 

 by Mr. Charles E. Austin, C.E., F.G.S., who collected them, in 1848, near Tourga 

 (lat. about 51° 30' N., long. 116° E.), from a cliff about 10 or 15 feet high, forming the 

 western bank of the small stream Burka, flowing southward into the River Onon, at a 

 distance of about 200 versts (about 133 miles) south-by-east from Nerchinsk, and 

 between Tourga, Nerchinsk (or Nertschinsk), and Adoon-Zabor. 



From information communicated by Mr. Austin I learn that on the bank of the stream, 

 between the rising ground (above 100 feet high, formed chiefly of a gravel of augitic 

 porphyry) and the stream, a shaft was sunk to examine the strata and to get specimens ; 

 and this penetrated — 1st, some alluvium ; 2nd, gravel of trap-rocks, with layers of soft 

 clay and broken indurated shale, 2 feet 6 inches ; 3rd, broken indurated shale, 1 foot 

 6 inches ; 4th, white clay, 2 feet ; 5th, slabs of the indurated fossiliferous shale in soft 

 clay, I foot 6 inches ; 6th, ferruginous clay, 1 inch. These beds seemed to dip Avest- 

 wardly at an angle of 25°. About 300 yards to the north of this spot, under a similar 

 gravel, shale-beds, like the former, but unfossiliferous, intercalated with clay, 18 

 inches thick, and underlaid by 6 inches of rounded trap-detritus, are raised up and 

 broken by a boss of basalt ; these continue for some distance northwards in the bank of 

 the stream, and ultimately disappear under a cliff of brown earth or volcanic tuff. On the 

 eastern side of the stream is a plain, with outbursts of augitic porphyiy, with asbestose 

 serpentine, basalt, and greenstone, bounded by granitic hills running north and south, and 



1 Middeudorf's term " Shells" here is equivalent to "Crustaceans" just below. He wrote this notice 

 of the locality after Miiller had recognised the Crustacean character of what he had previously been used 

 to look upon as molluscs. Besides, there were no real shells found except the obscure Paludina. 



2 It is to be remarked that almost all the known Estherian marls, shales, or mud-stones, are more or 

 less micaceous, and therefore formed in quiet waters, where currents have ceased. 



15 



