166 



In the Cote-d'Or, M. J. Maktin recognises the following 

 divisions : — 



a Mames jaunatres a Ammonites mucronatus, d'Orb. 



b II brunes a Turbo subduplicatus, d'Orb. 



c " et calcaire mameux a Ammonites complanatus, Brug. 



d Calcaire mameux et Mames scbisteuses a Ammonites serpentinus, Schloth. 



M. Martin's cabinets contained a good collection of the 

 Ammonites from these beds, among which I found Am. hifrons. 

 Am. serpentinus, Am. com-planatus, Am. Holandrei, representing 

 the species found in beds c and d ; and Am, Thouarsensis, Am. 

 radians, Am. insignis. Am. variabilis, Am. mucronatus, the species 

 belonging to beds a and h. Now this assemblage of Ammonites, 

 and the stratigraphical distribution of the species in the beds, 

 was of great interest to me, as I have long maintained, in papers 

 and discussions in our Club, that if the Cotteswold HiU sections 

 of Upper Lias were to be read correctly we must go to France 

 to learn the true character of their Toarcien types. When 

 examined palseontologically the Thouars section admits of a 

 sub-division into two stages, the beds a, h, c, d, forming the 

 upper, and the beds e, f, g, h, i, the lower zone ; and this is 

 precisely the condition which prevails in some of our most 

 typical sections, as at Frocester Hill, (Fig. IV,) where I include 

 all the marly, argillaceous, and arenaceous deposits found 

 between the Marlstone and Inferior Oohte in the Upper Lias, 

 and group these beds into two stages, each containing a special 

 fauna. The lower is in general an argillaceous formation, 

 with occasional and inconstant bands of calcareous nodules. 

 The shells of this division are nearly all specifically distinct 

 from those of the Marlstone on which it rests. The Ammonites 

 of the group Capeicorni, which formed so striking a feature in 

 the life of the Middle Lias, are all absent from the Upper Lias 

 beds, and in their stead have appeared great numbers of species 

 belonging to the groups Falciferi and Plantjlati. In England 

 one of the most dominant forms is Ammonites communis, Sow., 

 from which I have derived the name of this zone. 



The upper zone is mostly an arenaceous formation in 

 Gloucestershire, and partly an argillaceous one in Yorkshire, 



