178 ME A. RENDLE SHORT ON RHJ3TIC [May 1904, 



The Black Shales are about 15 feet thick : the fossils in them 

 are the best that I have ever seen. Below come about 15 feet of 

 yellowish marl and then red sandstone, but this part of the section 

 was very indifferently exposed. 



The horizon of the Cotham Marble is interesting-. It is remark- 

 able that at the very birthplace of the name, so little good 'land- 

 scape-stone ' should be found. Instead, there arc several large, flat 

 concretions of a texture very like that of Cotham Marble, about 

 1| feet in diameter and 4 to 6 inches thick, revealing cavities 

 in their interior, lined with calcite and containing the rare mineral 

 baryto-celestine, of a pale-blue colour, in which the sulphates of 

 strontium, barium, and calcium are all found. 



The beds K & L are of considerable interest also. They are much 

 more massive than at Redland, and show no ripple-marks or sun- 

 cracks. It is remarkable how the Naiadita keeps to special 

 horizons containing no other fossils. Careful search failed to reveal 

 Estheria minutct. 



Finally, we may note the apparent absence of the Bone-Bed. 



(D) Aust. 



It may, perhaps, be thought that on so classic a section as Aust 

 nothing new could have been written. For many years it has been 

 one of the type-exposures of the Rhaetic, and Agassiz had immor- 

 talized its vertebrate fauna long before the Bhsetic Beds were 

 recognized as a formation. The principal references to Aust are by 

 Agassiz (' Poissons Fossiles '), Etheridge (15), Davis (29), and the 

 Clifton-College Scientific Society (18). Of these, the detailed 

 account of the stratigraphy is given by Etheridge, whose table I 

 copy and supplement. Now in this table a vacancy of 13 feet was 

 left at the top, in a most interesting series of beds, because they 

 were inaccessible from below. I therefore had myself let down 

 from the top of the cliff by a rope, measured this gap, and 

 studied its contents both in place and in fallen pieces : — 



Nil. Feet indies. Formation. Fossils. 



23. 3 Blue Lias Ostrea liassica, 0. multicostata, 



Pleuromya Crowcombeia, Pectctt 

 Pollux. 



22. o to 8 Cotham Marble Modiola minima, Monotis decus- 



sata ; Gyrolepis Albertii, Pholi- 

 dophorus Higginsi, Saurichthys 

 apicalis, Legnonottis cotkamcnsis, 

 Spharodus minimus ; insect- 

 wings and elytra. 



21. 4 2 Yellow shaly clay (Barren.) 



20. 2 6 Hard, fine-grained, argil- Naiadita lanceolata; Estheria 

 laceous limestone, cream- min uta. 

 coloured outside, greyer 

 inside ; often fissile. 

 ID. 5 Yellow, thinly-bedded,very (Barren.) 

 argillaceous limestone, 

 often crumbly. 



