396 
SILUKIA. 
[Chaf. XVI. 
laden with fossils of the upper limestone. Hence the Prussian geologists, 
von Dechen, F. Romer, and Girard, have delineated these strata separately on 
exquisitely finished geological maps of the Rhenish Provinces of Prussia, the 
result of infinite research, applying to these rocks the name of ' the Agger and 
Lenne group ' *. This subdivision is another of the many proofs which patient 
inquiry has brought forth to demonstrate that it is not possible to form correct 
geological groups by appealing to mineral characters and superposition only. 
It is now known that the ' Agger and Lenne group ' is identical with those 
schistose courses on the left bank of the Rhine which, chiefly underlying 
the Upper Eifel Limestone, are known as the ' Calceolen-Schiefer.' There they 
are characterized by the presence of the Calceola sandalina, Cryphaeus (or Pleu- 
racanthus) punctatus, Cr. stellifer, Spirifer cultrijugatus, Sp. speciosus, Cyrtina 
heteroclita, and many other fossils which are common both in the Eifel country 
and in some of the limestones of South Devon. In following these formations 
into Belgium, a similar order of superposition is found to prevail.- 
Chief Eifel Limestone. — This is the great central calcareous mass which gives 
to the Devonian rocks their dominant and independent characters ; for, whilst 
the Lower Devonian of the Rhine exhibits, in some of its forms, analogies only 
to the Upper Silurian type, the limestone to which we have now ascended, and 
the approach to which is clearly indicated by the fossils in the preceding strata, 
contains a fauna which is unmistakeably peculiar, and wholly unlike that of the 
Silurian below or the Carboniferous rocks above it. One of the most striking Rhe- 
nish types of this rock is Stringocephalus Burtini, which is mainly characteristic 
of that which is now considered the uppermost band, as at Paflrath and Refrath 
on the right bank of the Rhine. The other prevailing fossils are Uncites gry- 
phus, Davidsonia Verneuilii, Spirifer undiferus and Sp. laevicosta, Megalodon cu- 
cullatus, Lucina proavia, Murchisonia bigranulosa, and the Corals Cyathophyl- 
lum caespitosum, Favosites polymorphus, Heliolites porosus, &c. 
Laden with a profusion of Corals, Crinoids, and other fossils, many of which 
have been made known through the beautiful work of Goldfuss, it is unneces- 
sary here to dilate further on the numerous organic remains of this limestone, 
many of which are common, as before said, in Devonshire. It may, however, 
be stated that, in the Eifel country as well as in the Harz, Coccosteus and other 
Ichthyolites have also been detected, which, as in Russia (see p. 362), serve to 
identify the rock as an equivalent of the central member of the Old Red Sand- 
stone of Britain. Among the organic remains are likewise several types which 
connect this band with the subjacent strata of Spirifer-sandstone, such as Pha- 
cops latifrons, Bronn, and Cryphseus punctatus, Steininger, with Spirifer spe- 
ciosus, Schloth., Sp. cultrijugatus, Rom., &c.f 
Upper Devonian of the Rhine Q Clymenia- ' and ' Goniatite-limestone,' von 
' Buch ' and Minister j ' Cypridinen-Schiefer,' Sandb. ; 1 Kramenzel-Stein ' and 
'Flinz' with 'Spirifer- Verneuilii-Schiefer,' &c, von Dechen). — The researches, 
however, of the able palaeontologists to whom allusion has already been made, and 
those of Prof, de Koninck in Belgium, have led to a clear separation of the lime- 
* This beautiful Map, which consists of 30 portion of the map had been executed by Dr. Gi. 
large sheets, ' Geognost. Karte der Ehein-Provinz rard, now Professor at Halle, 
una Westphalen,' is one of the noblest memorials f See the comparative table of Adolf Ebmer, 
of the school of Leopold von Buch, the great Geol.Kenntn.Nordw.Harzgebirgesin Dunkerund 
geological cartographer of the period ; and whilst von Meyer's Palaeontographica, vol. iii. p. 1, 1850. 
it does infinite honour to the Director of the Also the memoirs^of MM. Sandberger, Versteine- 
Survey (my eminent and valued friend, Geheim- rung. Ehein. Schichtensyst. : Nassau, 1850. And 
rath H. von Dechen) and his associates, is also a Frid. Sandberger, Geol. Verhaltn. Nassau (with 
proof of the enlightened encouragement of geolo- map) : Wiesbaden, 1847, &c. These works of MM. 
gical science by the Prussian Government. In Sandberger are full of accurate detail, 
the first edition of this work it was stated that a 
