﻿FRAAS ON THE JURA FORMATION. 



75 



Crustacea, Insects, Sepia, and Ammonece. In Swabia the great 

 quantity of Lobster-claws is everywhere characteristic, whence the 

 appellation of these limestones, and Fish-scales, Lumbricaria, Apty- 

 chus*, and Ammonites are also found. At some places, as near Ulm 

 and Einsingen, we perceive a transition into the Mollnsc-f acies. The 

 Vertebrata first begin to be abundant in Franconia ; where, how- 

 ever, there are so many local peculiarities, and so many shades and 

 transitions from one to another, that in a monograph of these forma- 

 tions a correct account of the localities is necessarily very important. 

 These local variations of the character of the rock without doubt de- 

 pended upon the influence of fresh-water ; which may also have 

 caused the fineness of the calcareous mud, the riband-like stripes 

 on the laminEe, and many other phcenomena. Fish are more espe- 

 cially found at Solenhofen ; but even here each of the numerous 

 quarries has its particular production. In one we find "Spiesse" 

 (lances) and "Sonnen" (suns) (Loliyines and Ammonites), in another 

 " Spinnen" (Spiders) and "Klauen" (claws) (Comatulce and Ap- 

 tychi), here Crustaceans, there Fishes, and so on. Eichstadt is 

 remarkable for the number of Insects (427 slabs with Insects are 

 exhibited in the Leuchtenberg Cabinet), Libellulcc, Cicadce, Cimices, 

 and Blattce ; there are also beds of Crustaceans, Fish, and Gorgonice 

 distributed in different quarries. Kelheim produces the finest Ptero- 

 dactyli, Aspidorhynchi, and other splendid specimens, the white 

 chalk-like matrix being here favourable to fossilization. As belong- 

 ing to this facies of the Upper " White Jura " in other countries we 

 might reckon Solothurn with its Turtles and Fish-teeth, and Tisbury 

 in Wiltshire, where Lobster-claws and Fishes are found in the neigh- 

 bourhood of coral-banks. 



Into so many different groups and local formations do we see the 

 last member of the Jurassic series divided ! How different the con- 

 ditions of these last, compared with the first beds — the arietes-beds — 

 of the " Jura!" The latter possessed a family of Ammonites with 

 millions of individuals, a Gryphcece- and Tkalassites-bed with innu- 

 merable specimens ; and these, in a homogeneous blue limestone, 

 uniformly spread through all the countries in which the "Jura" 

 appears ; — in the former, on the other hand, are found numerous 

 families, genera, and species from all the Classes of the Animal King- 

 dom ; and that, in strata of such manifold varieties, that the identity 

 of the rocks will no longer be found to agree in any two countries ! 

 If at any time, then surely in the Jurassic Period did the climate 

 make a giant-step in advance, educing multiplicity from out of a long- 

 lixed uniformity. With this climatal change the formation of Corals 

 in the Jurassic epoch is certainly connected. Where no Corals exist, 

 and where we find pure pelagic deposits in extended horizons, there 

 appears only the Mollusc-facies in its somewhat narrow boundaries, — 

 the characteristic condition of most of the Jurassic formations (Sequa- 

 nian, Kimmeridgian, and Portlandian) ; but where Coral-reefs are de- 

 veloped the different Faunae are called into existence. On the coral- 



* [See Strickland on Aptyclius, Quart. Journ. Geol. Soc. vol. i. Pt. I. p. 232, and 

 Von Buch and Burmeister on the same, ibid. vol. vii. Part II. p. 32. Also Von 

 Bueh, Bulletin Soc. Geol. de France, 2nd Scr. torn. vi. p. 566. — Transl ] 



