VOL. XVII. (I] NOTES ON A WHITE LIAS SECTION 47 



broken up rubbly beds of the White Lias (No. 3 in the photo- 

 graph PI. XIII. ; No. 12 in the section on page 48). The blue 

 clay below (No. 4 in the photograph, and No. 16 in the section) 

 contained bands of shale Uterally covered with Ostracoda. 



Attention should be directed to No. i in the section. 

 Throughout the best exposures which have come to my notice 

 in this immediate district that arenaceous band invariably 

 overhes the "Sun-Bed," showing a remarkable contrast be- 

 tween the dense white limestone beneath, which must have 

 been deposited in deep water, and the sandy deposit of shallow- 

 water origin above. The marine conditions must have altered 

 considerably-as indicated by the fossils— for whereas the 

 hmestone is almost destitute of organic remains, the arenaceous 

 shale above is crowded with Ostrea liassica. So that here, 

 it appears to me, is the dividing line between the Rh^tic White 

 Lias and the basement-beds of the Lower Lias above. 



The position of the Gotham Marble was not at first quite 

 clear. I came to the conclusion, however, that a certain 

 irregular indurated marly bed (No. 14 in the section), at the 

 base of the Rubbly Beds— the surface knobbly and the interior 

 veined with arborescent markings, resting on grey clay (No. 

 I5)_represented the Gotham Marble. With reference to the 

 change of conditions between the Rhaetic and the Lower Lias, 

 ■it has been noticed that, whilst the latter beds teemed with 

 saurian hfe, the former presented no evidence of such life. The 

 White Lias shows evidence of slow deposition, and of having 

 been subject to erosion, as indicated by boring molluscs and 

 their impressions on its surface. Many of the beds and inter- 

 vening bands of clay were iron-stained and saturated with 

 water. If the Rhstic Series can be divided, as Mr L. Richardson 

 writes, into an upper and lower stage, in my opinion, the 

 beds above described, from the " Sun-Bed " (No. 3 on page 48), 

 but No. 2 in Plate XIII., to the solid bed No. 19, if not to 

 No. 22, form a good example of the Upper Rhretic. The 

 Pteria [Avicula)-contoyta-Beds, which were not actually ex- 

 posed in the section described, coming in below. 



