350 



The Spinatus Bed of Oppel, Wright, and other authorities 

 forms the uppermost Zone of the Middle Lias ; it rests upon 

 the Margaritatus beds, and is overlaid by the shales of the 

 Communis or Bifrons zone, with its Leptcena band a,nd clays, 

 which the author first brought to light in Gloucestershire in 

 1860, all these belong to the Upper Lias system. One question 

 important to broach at the outset, is this — whether the suc- 

 cession of beds called the Spinatus Zone is to be included in 

 the Upper or the Middle Lias, as opinions vary on the point. 

 To clear up this, must be my plea for dwelling so much in my 

 treatment upon minute details. An examination of the lias in 

 reference to this substage of life, will bring out the following 

 particulars, namely, that where as in the North Cotteswolds, 

 the sediments appear to have been deposited without serious 

 disturbing influences, the Spinatus Zone is clearly marked off 

 by its palaeontology. In other regions, where the deposits are 

 schistous, contorted, or irregularly faulted, as they are in 

 Germany ; — in Hanover according to Seebach, and in Brunswick 

 according to Emerson or Brauns; and again in France where 

 they show but feebly, owing to similar disturbing causes * there 

 such authors are unable to distinguish, and do not admit this 

 zone to be a distinct substage of the Middle Lias. 



On the other hand Dr. Oppel in his Jura formation explains 

 that in the Suabian provinces the Spinatus Zone can be fully 

 established. Another equally accurate and trustworthy authority. 

 Dr. U. ScHLONBACH vouchcs it to be for North West Germany 

 a zone clearly distinct ; for his discussion of it see Zeitschrift 

 der Deutsch. geolog. Gesellschaft, Berlin, 1870. f Returning to 

 the French Lias the strata do not seem to be easily separated, 

 either by M. Dumortier in the deposits of the Rhone district, 

 to the South and East, or on the North West of France by the 

 M. M. Deslongchamps. But we must bear in mind that their 

 Middle Lias occurs in positions that must totally preclude all 



* See A. D'Ai-chaic. Hist, des Prog, de la Geol, tome VI. p. 444, Paris 1854. 



t Also " Ueber den Eisenstein des mittlereu Lias im N. W. Deutschland Berlin, 

 1863. I have also consulted " Die Schichteufolge des unteren und mittleren 

 Lias in Norddeutschland. 1863," by the same author. 



