138 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 16, 



of contemporaneous porphyry and recomposed trappean shales ; and, 

 without noticing minute puckerings and undulations, they exhibit a 



Section II. 

 Llanberis. 



Stratification of Mr. Assheton Smith's Quarries. 



Old quarry 



a. Sandstone. 

 a'. Coarse slate. 



b. Upper blue slate. 



c. Hard ferruginous bed. 



Level of Llanberis lake. 



d. Red slate. 



e. White bands. 



/. Lower blue slates. 

 g. New quarry. 



great synclinal, and afterwards an anticlinal line (which cuts through 

 the Penrhyn and Llanberis quarries), and afterwards, at their eastern 

 and upper surface, plunge unequivocally under a vast thickness of 

 beds, composed of coarse greywacke, slate, felspar rock, trappean 

 shales, talc slate with asbestus, greenstone, &c. &c. ; the whole mass 

 being most distinctly stratified, and inclined to E.S.E. at a great angle, 

 on the average not less than 50°. I hope in a future communication to 

 describe this great ascending section in more detail, as affording a 

 striking instance of the alternation of aqueous and igneous deposits, 

 and of deposits having a character intermediate between the two. 



Counting from the zone of the Penrhyn slates, we have a regular 

 ascending section for more than two miles measured on a horizontal 

 line transverse to the strike of very highly inclined beds. We then 

 meet with a great synclinal trough, which I have traced from Car- 

 nedd Llewelyn, Glyder Fawr, Snowdon, and Moel Hebog, a distance 

 along the crest of the chain of about fifteen miles. Bands of fossils* 

 * Fossils from Llyn Ogwen — 



Orthis like calligramma. 



vespertilio. 



cambriensis. 



Murchisonia scalaris (angulata, former lists). 



Favosites fibrosa. Encrinite stems. 



Orthis flabellulum. 



)■ Snowdon. 



— Actonise. 



— expansa. 



— elegantula. 

 Encrinites. 

 Turbinolopsis bina. 

 Orthis expansa. "I 



— Actonige. I ht i tt i 

 -flabellulum. f^^^^'^^b^g- 



— elegantula. J 



)ina. J 



