30 LA TOUCHE : GEOLOGY OF WESTERN RAJPUTANA. 



to the north-east, parallel to the Aravalli range, the basin extended,. 

 at least at intervals, as far as Khari, 40 miles to the north-east of 

 Bikanir, and 150 miles from the present southern limit of the sand- 

 stones near Jodhpur. 



So far these rocks have yielded no traces of indubitable organic 

 remains, but in the neighbourhood of the village of Osia, 30 miles 

 north of Jodhpur, I found on the lower surface of seme of the fine 

 grained sandstone beds at a particular horizon, certain markings 

 which I find it difficult to reconcile with any other than an organic 

 origin. They are evidently casts of grooves on the upper surface of 

 the underlying beds, but the latter appear to bave been of a soft 

 clayey nature and all trace of the actual grooves has disappeared. 

 The casts are in the form of straight or curved ridges, occasionally 

 duplicated, with a rounded cross section, very slightly raised above 

 the surface of the slabs on which they occur and about one-eighth 

 of an inch in width. They are sometimes parallel, but frequently 

 cross each other in all directions. The resemblance of the straight 

 ones especially when they tail off gradually at the ends, as they often 

 do, to mechanically formed striae, is very striking, and it is possible 

 that they may have been produced by some mechanical means, but it 

 is very difficult to conceive what the agent can have been. They are 

 certainly not worm tracks ; they are not such markings as would be 

 made by large grains of sand or small pebbles, besides no such 

 pebbles are to be found in the beds in which they occur. Floating 

 vegetation just grazing the bottom ; the tips of fronds of algae or 

 reeds sweeping to and fro under the influence of gentle currents in 

 shallow water ; or possibly the fins of fish swimming within a short 

 distance of the bottom are explanations that have suggested them- 

 selves to me, but none of them are satisfactory, especially because 

 if the markings were due to either of these causes we should certainly 

 find traces at least of the vegetation or of the fish preserved in these 

 fine grained sandstones, and a diligent search has revealed absolutely 

 ( 30 ) 



