TRANSACTIONS OF SECTION C. 653 



The author proposed to apply to all these problematical plants, having a tissue 

 of vertical and horizontal tubes, the general name Nematophytece or Nematophyton. 



The paper referred to the history of opinion on these objects and the biblio- 

 graphy of the subject; but this, as well as detailed descriptions, are omitted in this 

 abstract. 



3. On BiloUtes. 5// Professor T. McKennt Hughes, ilf.^., jP.G.S. 



The author pointed out that the views of previous writers on this subject might 

 be grouped generally under two heads : — 



1. One was that the fossils in question represent a solid organism, which had 

 been buried in the sand or mud, and had left only the cast of its body ; that the 

 organic matter had all disappeared and the form had been modified hj the various 

 changes which the rock had since undergone. Some believed that nereites, for 

 instance, was the actual cast of the body of a marine annelid allied to nereis, while 

 others considered that all such bilobites as Cruziana were the impressions of 

 portions of marine algae. 



2. Another view was that all the fossils such as those above mentioned were 

 tracks left by animals on 'the surface of the sand or mud, and filled by the next 

 flood with sand, which took the east of the depression. 



It had been observed by various previous authors that the bilobites were some- 

 times in relief on the upper side of the slab as it lay in place, and this was urged 

 as evidence that in some cases, at any rate, they represent solid cylindrical bodies 

 like the stems of some well-known sea-weeds. 



He had examined the typical sections in Nantffrancon, where the Ci-uziuna 

 semiplicata was the characteristic fossil, and found that it was always in relief on 

 the upper side of the slab (except where so compressed that the upper and lower 

 sides of the cylindrical body were both driven in, so as to give a double down- 

 curved surface). The side ornamented with the herring-bone pattern was the 

 upper side ; the lower was a smooth longitudinally furrowed groove. 



He had found somewhat similar tracks in beds of sandstone in the mountain 

 limestone in Westmoreland, where the tracks were in high relief on the upper side 

 of the slabs, and when this compressed cylindrical body was removed a smooth 

 shallow track was seen in what had been the surface of tbe sand. The ornamented 

 side was uppermost. The layers of sand, instead of thinning out against this ridge- 

 like body, were lifted over it without any appreciable diminution of thickness, so 

 as to appear, not so much as if they had been laid down over this cylindrical body, 

 when it was lying on a sandy surface, but rather as if they had been lifted so as 

 to form an arched tunnel by the protrusion of some solid body, such as a burrowing 

 animal, between the layers of previously deposited sand. There were different 

 patterns on successively overlying layers, as if the effect of continuous scooping 

 work was more apparent on the lower, and the periodic lift-forward of the animal's 

 body chiefly affected the upper layers. There were also holes at regular intervals 

 from the median groove of the bilobite passing up through two or three of the 

 superincumbent layers. 



He observed further that in the same beds there were plants with the car- 

 bonaceous matter still preserved : and from this he inferred that, had there been 

 any vegetable tissue around the bilobites, there was no reason why it should have 

 disappeared in that case only. 



On the whole, he arrived at the conclusion that the bilobites he exhibited were 

 neither vegetable remains nor the surface tracks of animals, but were the burrows 

 of animals which bored between the layers of sand, packing their tunnels behind 

 them with the sand excavated in front, and that at regular intervals they com- 

 municated with the surface by means of the holes observed passing throuo-h the 

 overlying layers. He considered that the observations of Albany Hancock on the 

 burrowing Crustacea at the mouth of the Tyne offered the best explanation of the 

 phenomena, and would extend his inferences. 



