750 STRATIGRAPHICAL GEOLOGY. [Boox VI. 
{In the Mississippi basin where the sub-Carboniferous groups are best 
developed, they present the following subdivisions in descending order : 
Chester group.—Limestones, shales, and sandstones, sometimes 600 feet. 
St. Louis group.—Limestones with shale, in places 250 feet. 
Keokuk group.—Limestone with chert layers and nodules. 
Burlington group.—Limestone, in places with chert and hornstone, 25 to ~ 
200 feet. 
Kinderhook group.—Sandstones, shales, and thin limestones, 100 to 200 
feet, resting on the Devonian black shale. 
| The sub-Carboniferous groups are mainly limestones, but contain here 
‘and there remains of the characteristic Carboniferous land vegetation. 
| Crinoids of many forms abound in the limestones. A remarkable polyzoon, 
4 | Archimedes, occurs in some of the bands. The brachiopods are chiefly 
represented by species of Spirifera and Productus; the lamellibranchs by 
Myalina, Schizodus, Aviculopecten, Nucula, Pinna, and others; the cepha- 
lopods by Orthoceras, Nautilus, Goniatites, Gyroceras, &. The European 
genus of trilobite, Phillipsia, occurs. Numerous teeth and fin-spines of 
selachian fishes give a further point of resemblance to the European Car- 
boniferous Limestone. Some of the rippled rain-pitted beds contain 
{amphibian foot-prints—the earliest American forms yet known. 
-Carboniferous. 
Su 
Section V.—Permian or Dyas. 
§1. General Characters. 
The Carboniferous rocks are overlaid, sometimes conformably, 
but in Europe for the most part unconformably, by a series of 
red sandstones, conglomerates, breccias, marls, and limestones. These 
used to be reckoned as the highest part of the Coal formation, In 
England they received the name of the ‘‘ New Red Sandstone” 
in contradistinction to the “ Old Red Sandstone” lying beneath the 
Carboniferous rocks. The term “Poikilitic” was formerly proposed for 
them, on account of their characteristic mottled appearance. From 
their wide development in the Russian province of Perm they were 
styled “ Permian” by Murchison, De Verneuil, and Keyserling. In 
Germany, where they exhibit a well-marked grouping into two great 
series of deposits, they have received the name of “ Dyas.” In North 
America, where no good line of subdivision can be made at the top 
of the Carboniferous system, the term “ Permo-Carboniferous” has 
been adopted to denote the transitional beds at the top of the 
Paleozoic series, | 
In Europe two distinct types of the system can be made out. In 
one of these (Dyas) the rocks consist of two great divisions: (1) a 
lower series of red sandstones and conglomerates, and (2) an upper 
group of limestones and dolomites. In the other (Russian or 
Permian) the strata are of similar character but are interstratified 
in such a way as to present no twofold petrographical subdivision. 
Rocks.—The prevailing materials of the Permian series in 
Europe are undoubtedly red sandstones, passing now into conglo- 
merates and now into fine shales or marls. In their coarsest forms 
these detrital deposits consist of conglomerates and breccias composed 
of fragments of different crystalline or older Paleeozoic rocks (granite, 
diorite, gneiss, mica-schist, quartzite, greywacke, sandstone, &.), that 

