800 - -STRATIGRAPHICAL GEOLOGY. — [Boox VI. 
fineness of grain has enabled it to preserve in the most marvellous perfec- 
tion the remains of a remarkably varied and abundant fauna both of the sea 
and land. Beside skeletons of fishes (Aspidorhynchus, Lepidotus, Megalurus), 
cephalopods showing casts of their soft parts, crabs with every part of 
the integument in place, and other denizens of the water, there le the 
relics of a terrestrial fauna washed or blown into the neighbouring 
shallow lagoons—dragonflies with the lace-work of their wings, and other 
insects, the entire skeletons of Pterodactyle and Rhamphorhyncus, in one 
case with the wing membrane preserved, and the remains of the earliest 
known bird, Archeopteryx (see pp. 778, 781). The German Purbeck 
group attains an enormous development in Westphalia (1650 feet), where 
between limestones full of Corbula, Paludina, and Cyclas, pointing to 
fresh-water deposition, there occur beds of gypsum and rock-salt. 
Alps.—The Jurassic system in the Alps is not so well developed as in 
other parts of Hurope. The Lias is there recognizable by fossils which 
in their specific forms and general succession may be paralleled in a broad 
way with those of the same formation elsewhere. It lies conformably 
on the Rhetic, but between it and the overlying Jurassic groups 
there is a marked unconformability. At the top of the Alpine Jurassic 
series an important group of deposits occurs to which the name of Titho- 
nian stage was given by Oppel.' Much discussion has arisen as to 
whether this stage should be referred to the Jurassic or Cretaceous system. 
The geologists of Bavaria and Austria assign it to the former, while those 
of France place it with the latter. According to the one view the base 
of the group is marked by the zone of Ammonites (Oppelia) tenuilobatus 
(Aspidoceras acanthicum), over which comes a mass of strata consisting 
sometimes of reddish well-bedded limestones so full of Terebratula diphya 
(jamtor)as to be named the “Diphya-limestone;” sometimes of thick-bedded 
or massive light-coloured limestones (Stram berg limestone, from Stramberg 
in Moravia). The limestones are often crowded with cephalopods, of 
which a large number of species, many of them peculiar, have been 
noticed. The shales or impure shaly limestones are sometimes full of the 
curious cephalopod-appendages known as Aptychus (Aptychus-beds). 
Some of the more massive limestones are true coral reefs. On the other 
hand, it is contended by M. Hébert and other veologists of France that 
the position of the zone of Amm. tenuilobatus has been mistaken. He 
believes that this zone is really more ancient than the Coral-rag of the 
North, and that the limestones with Terebratula diphya and a large 
cephalopodous fauna are certainly Neocomian. ‘The Diphya-limestone 
with its peculiar fossils appears to range from the Carpathians through 
the Alps and Apennines into Sicily. 
North America.—So far as yet known, rocks of Jurassic age play 
but a subordinate part in North American geology. Perhaps some of 
the red strata of the Trias belong to this division, for it is difficult, owing 
to paucity of fossil evidence, to draw a satisfactory line between the two 
systems. Strata containing fossils believed to represent those of the 
Kuropean Jurassic series have been met with in recent years during the 
explorations in the western domains of the United States. They occur 
' Zeit. Deutsch. Geol. Ges, xvii. (1865), 535. See also M. Neumayr, Abhandl. Geol. 
Reichsanstalt. y.; Zittel, Palwont. Mittheil. Mus. Bayer. ; Hébert, Bull. Soc. Géol. France, 
ii. (2nd Sér.), 148; W. Benecke, Trias und Jura in den Sudalpen, 1866; C. Moesch, 
Jura in den Alpen, Ostschweiz, 1872. See also the Jura-studien, of Neumayr, already 
cited (p. 784). 
