228 



and green marls, 23 feet extra will be extracted from the upper part 

 of the Keuper, and added to the now-called Rhsetic above, thus 

 making the Coombe Hill section 60 feet in thickness. The Estheria 

 band is succeeded by two well-marked series of clays and marls, Nos. 15 

 and 16, which physically differ so much, as to demand distinct recognition, 

 and which must be divided to be understood. The lower group, (No. 15 

 in the section,) consists of grey fissile marls with numerous thin pyritic 

 Limestone bands containing few fossils. These marls give good evidence 

 of having then accumulated xmder estuarine and shallow water conditions. 

 I seai'ched for Estheria in the thin calcareous bands wliich are associated 

 with the marls, but failed to detect any; and it appears to me, that here, 

 as well as at all other sections where the Estheria Zone is defined, that 

 the white marly band below (No. 14) is the uppermost limit of the distri- 

 bution in time, of this gregarious species of the Phyllopod Limnadidse, 

 Estheria miniita. 



No. 16 is composed of numerous beds of indurated, bi'own, clayey, 

 shaly marls. Fish scales and teeth are scattered through the sei-ies, 

 and especially so about the middle of the beds, where a tolerably well- 

 defined indurated band indicates their presence abundantly; and this 

 horizon is more fissile than the portions above and below. Dividing bed 

 15 from 16 is a thin rusty band evidently possessing an excess of pyrites, 

 and which clearly divides the grey pyritic Shales, No. 15, from the 

 argillaceous Clays, No. 16 above, at the top of which, new features, both 

 physically and Palreontologically come in and carry us up to those 

 conditions, so familiar to all, as occurring at the base of the Lias. This 

 change is first indicated by the presence of an indurated bed of cream- 

 coloured, marly, argillaceous Limestone, (No. 17 in section,) composed 

 entirely of Myacites Musculoides, Schl., and Modiola minima, Sow., 

 and although only two inches in thickness, this bed will always be of 

 interest, from the abundance of these two species contained in it. Above, 

 and united to this by a slight parting at its upper surface, is the well- 

 known Monotis bed, No. 18, kept distinct from No. 17 on Palajonto- 

 logical grounds. This zone, although only three inches in thickness, is so 

 important and well-defined that it demands especial notice ; the thin 

 fissile Limestone slabs which, united, make up the measurementof the three 

 inches, are literally ci'owded with the small huihe&utiiviX Monotis(Avicula) 

 decussata, Goldf.; it is here ubiquitous, occxirring in thousands over 

 the surface of the slabs. The matrix in which they are embedded is 

 as smooth and even in its texture, as the lithographic stone of Solenhofen, 

 and has the conchoidal fracture peculiar to this and the Gotham marble ; 



