GEOLOGICAL SOCIETY OF DUBLIN. 21 



The commonest tracks, however, are those first mentioned, which are to be 

 found in the greatest numbers in the beds over and underlying beds of 

 Oldhamia radiata, though found even intersecting these beds themselves. 

 One track was found which could be traced from the red bed beneath the 

 Oldhamia, and through, or at least into, a red bed above the Oldhamia. 

 The system of beds in which they are most abundant, as seen here, is 

 generally 5 feet thick, and made up as follows : above and overlying 

 the system, a layer of green quartzose rocks of compact texture, having 

 its surface in parts ripple-marked, and overlaid by a layer of Oldhamia 

 radiata ; next a bed of red shaly slate, often much disintegrated, with 

 slight traces of Oldhamia and a few vertical tracks ; next, a red gritty 

 slate, with black points scattered through it, the tubuli few, and gene- 

 rally of the kind with tapering extremities ; next, a compact bed of red 

 slate, intersected in every direction with tracks ; the whole bed, as it 

 were, knit together by them ; next, a layer of Oldhamia radiata, pale- 

 grayish in its colour, from 0-25 inch to 3 inches in thickness ; tracks 

 generally few in number (this bed sometimes more or less stained with 

 red) ; next, a bed of red shaly slate or compact red slate; tracks in the 

 former case few and vertical ; in the latter numerous ; then a red fissile 

 slate bed, in which I did not detect any tracks (this bed often want- 

 ing) ; then the gritty red bed : — this system, with slight variations, 

 occurring three or four times over, and resting on the green quartzose 

 rocks. 



In many places the red beds are much thinned out, and occur only 

 as veins three or four inches thick. 



Short vertical tubuli (vide Plate I.) occur in nodules, which are abun- 

 dant in the green quartzose beds in parts. Mr. Salter, who accompanied 

 me here on one occasion, pointed out, on the lower face of one of the 

 beds, rounded knobs corresponding to the cupped termination of the 

 tubuli and rounded elevations, casts of trails of worms on the top of 

 the mud. He also obtained one or two imperfect specimens of these 

 last in the white quartz rocks, which here protrude. Though frequently 

 found crossing, on careful examination I was unable to detect any 

 branching among these tubuli. When closely examined they are found 

 to be made up of concentric lamina?, of about the thickness of ordinary 

 writing-paper, depressed in the centre, like a pile of watch-glasses. In 

 every instance the tubuli are found to be of a different colour and tex- 

 ture from the surrounding rocks, as though their contents had undergone 

 some chemical or other change, such as we know is communicated by 

 recent Annelidans to the sand which passes through their bodies. In 

 some instances the rock in immediate contact with the tubuli was found 

 to be stained of a darker colour, like that which is frequently found in 

 the circumference of the burrow of Arenicola ; this is chiefly seen in the 

 rounded, tapering tubuli. 



The vertical tubuli found in the quartzose rock differ in shape from 

 the others here described, tapering gradually from above downwards. 

 Even after a very careful examination I could not satisfy myself as to 

 whether any of these animals possessed a tube or not ; if they did, it 

 must have been membranous, and many things about the tracks seem 



