J. W. Davis — On a New Fossil Fish Spine. 531 



may not be more than usually tough in these places. Generally 

 the rock seemed to me to be of a character easily disintegrated. 



How then were the roads formed? Obviously by the planing 

 action of waves acting on the rock and cutting the shore-line back. 

 Subsequently, on the lowering of the water-line, the detritus of the 

 mountain side falling, and being washed down hill by rain, etc., 

 lodged on the platform of the shelves, and there accumulating 

 gradually formed, a pile of loose material sloping towards the 

 valley, and slowly obliterating the true roads. 



I add a sketch of the profile of the mountain side, as seen from 

 the big gill looking up the valley. It will be seen that my profile 

 is quite similar to the diagram given from Macculloch by Sir John 

 Lubbock in the Q.J.Gr.S. for 1868, vol. xxiv., with this remarkable 

 difference : in my sketch the two highest roads are represented as 

 comparatively near to one another, while the lowest is much lower 

 down ; this is the case in nature ; the average heights of the roads 

 above sea-level being, according to the Ordnance Surveyors, 1148, 

 1067, and 855 feet; but in Sir John Lubbock's diagram, after 

 Macculloch, the two lowest roads are represented as close together, 

 and the third much higher up : the diagram has evidently been 

 drawn or printed upside down ; for turn the book topsyturvy and 

 the diagram is right. 



As to the nine points then, on which, according to Sir John Lub- 

 bock, we have a substantial agreement, the whole question of the 

 true nature of the roads turns upon the second and third : these I 

 would controvert thus : the horizontal roads are shelves cut out of 

 the solid rock ; and these shelves only appear when the solid rock 

 itself appears, being in other cases entirely hidden by the debris of 

 the mountain side, which has fallen and accumulated upon the shelves. 



It is further to be noted that the disintegration of the rock forming 

 the shelves would in course of time disguise the fact that the roads 

 consisted of rock shelves, and cause them to appear as mere heaps 

 of detritus. 



II. — Description of a New Species of Fossil Fish Spine, 

 Ctenacanthus minor, from the Lower Coal-measures of 

 Yorkshire. 



By James W. Davis, F.L.S., F.G.S., etc. ; 

 Hon. Secretary of the Yorkshire Geological and Polytechnic Society. 



ASHOET time ago, whilst examining and appending the names 

 to a number of specimens of fossil fish in the collection of 

 the Bradford Philosophical Society, which are being arranged and 

 exhibited in the new Corporate Museum in that town, I came across 

 the spine which is the subject of this notice. It is from the Black- 

 bed Coal at Dudley Hill, near Bradford. It was associated with a 

 number of fish remains, amongst others : — 



Ctenacanthus hybodoides, Egerton. 

 Gyracanthus formosus, Agass. 

 Pleuracanthus Icevissimus, Agass. 

 Diplodus gibbosus, Agass. 

 Ctenoptycliins, sp. 



Petalodus Hastingsice, Agass. 

 Acanlhodes, sp. ? 

 Megalichthys Eibberti, Agass. 

 Coslacanthus Upturns, Agass. 

 Rhizodus Hibberti, Agass. 



