798 
STRATIGRAPHICAL GEOLOGY. — [Boox VI. 
Pentacrinus Buvigniert, Heteropora conifera; 2. Beds with Terebratula 
obovata, Isastrea limitata; 3. Beds with Terebratula cardium, Apiocri- 
nites Parkinsoni; 4. Thick-bedded limestones with Rhynchonella deco- 
rata; 5. Oolitic limestones with Pecten laminatus; 6. Marls with Ostrea 
acuminata. 
Bajocien, or Oolithe Inférieure, well developed in the Department of Cal- 
vados, the name of the group being taken from Bayeux. In the north 
of France the strata are divisible into two zones, the lower characterized 
by Ammonites Murchisonz, the upper by A. Blagdeni, &c. In the east of 
the country this group covers a large area. In the department of Sadne. 
et-Loire it contains the following subdivisions in descending order— 
1. Thin-bedded oolitic limestone perforated by Lithophaga bajocensis ; 
2. Ferruginous and oolitic limestone with OCollyrites ringens, Ammonites 
Parkinsoni, A. subradiatus, A. garantianus; 3. Sandy marls and calcareous 
bands, Terebratula Phillipsii, Rhynchonella (numerous species), Ammonites 
interruptus, A. Truellet, &c.; 4. Coral-limestone composed of reefs of Tham- 
nastrea, Isastrea, &c., with Ammonites Sauzet, Pinna inornata, Rhyncho- 
nella costata, &c.; 5. Reddish or white thick-bedded limestone (Caleaire & 
Entroques) with thin marly beds full of sponges, polyzoa, and fragments 
of crinoids, Ammonites Murchisonx, Belemnites giganteus, Pholodomya fidi- 
cula, Trigonia striata, &c.; 6. Brown siliceous limestone with Pecten perso- 
natus, resting upon ferruginous sands containing Ammonites opalinus, 
which form the top of the Lias. ; 
Toarcien (from Thouars = Upper Lias), composed of alternations of lime- 
stone and clays capable of paleontologica] separation into an upper series 
containing Ammonites opalinus, A. thouarsensis, A. radians, A. insignis, 
A. variabilis, A. mucronatus ; a middle series with A. radians, A. bifrons ; 
and a lower series with A. serpentinus, A. complanatus, Rhynchonella 
tetrahedra. 
Liassien (= Middle Lias), composed of marls and argillaceous limestones 
divisible into a series of zones characterized by many of the same Ammo- 
nites as the Middle Lias of England. 
Sinémurien (= Lower Lias), composed of argillaceous limestones, and marls 
with the normal series of Ammonite zones. Ostrea arcuata, Belemnites brevis. 
Hettangien (Infra-Lias), marly and shelly limestones with Ammonites 
planorbis, &c., and corresponding to the Angulatus and Planorbis zones 
at the base of the Lias, resting conformably on the sandstones, marls, and 
bone-bed of the Avicula contorta zone or Rheetic. 
One of the most interesting features of the Lias in the northern or 
Jura part of Switzerland is the insect beds at Schambelen in the Canton 
Aargau. The insects are better preserved and much more varied than in ~ 
the English Lias, and include representatives of Orthoptera, Neuroptera, 
Coleoptera (upwards of 100 species of beetles), Hymenoptera, and Hemi- 
ptera. About half of the beetles are wood-eating kinds, so that there must 
have been abundant woodlands on the Swiss dry land in Liassic time.} 
In north-western Germany the subjoined classification has been 
adopted :? 
1 Heer, Urwelt der Schweiz, p. 82. 
Upper or White 
( Purbeck group (Serpulit, Miinder Mergel), forming a transition between 
at Purbeck and Portland. 
g | Eimbeckhauser Plattenkalke and zone of Amm. giganteus, equivalent 
"2 to the English Portland. 
& 4 Kimmeridge group (Upper, with Hxogyra virgula ; Middle or Pteroceras 
- beds; Lower or Astartian with Nerinwa beds and zone of Terebratula 
= humeralis *). 
™ | Oxford group (Upper or Corallian, with Cidaris Jlorigemma ; Lower or 
\ Oxford [Hersumer schichten], with Gryphxa dilatata). 


2 Heiny. Oredner, Ober. Jura in N. W. Deutschland, 1863. See also the works 
of Oppel and Quenstedt quoted on p. 784, and K, von Seebach’s Der Hannoversche Jura, 
1864. 
Brauns’ Unter., Mittl. und Ober. Jura, 1869, 1871, 1874. 
® Struckmann, N. Jahrb. 1881, p. 102. 
