314 Geological Society. 



of the rock ; and he expressed his belief that they were made by 

 some animal when " the land was submerged to the extent indicated 

 by the altitudes at which they occur." From their position he 

 supposed their formation to have taken place during, or imme- 

 diately before the Glacial epoch. 



Mr. J. Gww Jeffkeys remarked that Mr. A. Tylor had already 

 called attention to the same subject three years ago. He could not 

 agree in regarding the markings as lithodomous borings. The borings 

 of Saxicava and Gastrochcena were not parallel, but enlarged to- 

 wards the base into a pear-shaped form. They were also compara- 

 tively straight, and not curved or bifurcated as in the limestones 

 exhibited. The range in height was also against their being the 

 work of marine mollusks. He thought the perforations were more 

 probably due to atmospheric agency. 



3. " On the Parallel Roads of Glen Roy." By Prof. James JSicol, 

 F.R.S., F.G.S. 



The author briefly noticed the two principal hypotheses which 

 have been advanced to account for the formation of these terraces, 

 and asserted his own belief in their marine origin. He rested his 

 argument against the hypothesis of their lacustrine origin chiefly 

 on the ground that if their formation be due to successive pe- 

 riods of repose alternating with sudden drainings of a lake occupy- 

 ing the present valley of Glen Roy, we ought still to 'find traces of the 

 violent debacles occasioned by these drainings, or of large rivers in 

 the gorges through which the waters must have flowed. The author 

 stated that no such appearances presented themselves ; on the con- 

 trary, he adduced certain characters exhibited by these gorges, 

 which, he considered, were strongly in evidence of long-continued 

 sea-action, and seemed to indicate that the gorges in question had 

 been occupied, at the time of the formation of the terraces, by arms 

 of the sea. 



Mr. H. M. Jenkins objected to the supposition of the sudden 

 alteration in the level of the water adopted by the author. He 

 thought the gradual sinking of the water was quite compatible with 

 the formation of the roads. He instanced the formation of terraces 

 in gravel-pits filled with water. 



Sir H. James announced that the Ordnance survey of the district 

 in question was now complete. 



4. " On Beds of supposed ' Rothliegende ' age near Knares- 

 borough." By J. Clifton Ward, Esq., P.G.S. 



The author called attention to certain beds occurring in the 

 neighbourhood of Knaresborough, especially at Plumpton, either of 

 a coarse and conglomeratic structure, or consisting of sandstones 

 or sandy shales. These beds have been regarded by some as be- 

 longing to the " Rothliegende " series ; by others as belonging to 

 the Millstone Grit. The chief arguments in favour of their be- 

 longing to the Millstone- Grit are, as stated by the author : — 1, 

 Their similarity to true Millstone- Grit beds ; 2, their occurrence in 



