DESCRIPTION 



OF THE 



FOSSIL OOLITIC ASTERIADiE. 



ON THE ASTERIAD^ OF THE LIAS. 



Before describing the Asteriadse of the Lias I purpose giving a short account of the 

 several zones of hfe into which this great formation is now divided, with the view of 

 accurately defining the statigraphical distribution of its Echinoderinata in time and 

 space. More ample details on the subject than my present limits permit will be found in 

 the various works cited in the synonyms prefixed to the description of the different zones. 



English geologists divide this formation into Upper Lias, Marlstone, and Lower Lias, but 

 these subdivisions require additions and modifications in order to place the liassic beds 

 of the British Isles in correct correlation with those of France, Switzerland, and Germany. 

 For on the Upper Lias clays, in certain localities, are superimpose^d extensive arenaceous 

 deposits, which, previous to the publication of my memoir on the Upper Lias sands,^ Avere 

 grouped with the Inferior Oolite, and in the Lower Lias are included several beds of clays 

 and marls which, with the Marlstone of English authors, forms the Middle Lias of conti- 

 nental geologists. 



Taking the Lias beds so well exposed in their natural order of superposition in the 

 north and south of England in the magnificent sections on the Yorkshire and Dorsetshire 

 coasts, and naming each group of beds by the most characteristic Ammonite contained 

 therein, we find the following zones of life, taken in descending order : 



The Upper Lias. — The sands of the Upper Lias forming the upper portion of this 

 zone, are characterised for the most part by Ammonites belonging to the group Falciferi, 

 as Ammo?iiies opalinus, Rein., and A. radians, Schloth. Ammonites Juretisis, Ziet., and 

 A. insignis, Schiibl., both belonging to other groups, are likewise associated with them. 



1 Pal^ontographical and Stratigraphical Relations of the so-called "Sands of the Inferior 

 Oolite," 'Quart, Jour, of the Geological Society,' vol. xii, p. 292, 1856. 



