30 ON CERTAIN VERMIFORM FOSSILS. 



we have seen tliat on the beach there are elevated, cylindrical 

 tracks produced by crustaceans not very dissimilar to those in 

 question. 



Can the two former or large species be worm-tubes or any 

 organic body ? The transverse striation on the surface of the 

 grooved form certainly gives to it much the appearance of some 

 organism. An endeavour, however, has already been made to 

 explain the nature of this peculiar character; but whether or 

 not successfully there is sufficient evidence to prove that these 

 fossils are not organic. The slabs exhibiting these vermiform 

 tracks are frequently marked with numerous small pits or punc- 

 tures which sink for a short distance beneath the surface. These 

 (PI. VI. c, c) hav^ somewhat the appearance of what have been 

 termed by geologists impressions of rain-drops. In this instance, 

 however, they are undoubtedly produced by the animals which 

 have made some of the smaller tracks, as it is not uncommon to 

 see the latter terminate in one of these punctures (c, c). Now, 

 it occasionally happens that the large or striated fossils are per- 

 forated by these punctures, and the scars thus made are similar 

 to those in like manner formed on the other parts of the slab. 

 This could hardly be so had the slab and the fossil been origi- 

 nally composed of two different substances — that is, had the 

 former been nothing but sand or mud, and the latter a worm- 

 tube or some other organic body. 



Another fact equally instructive may also be cited. The slab in 

 the Newcastle Museum previously alluded to, exhibits not only 

 the large grooved track, but also several of the small furrowed 

 one, and the latter frequently pass over the former in various 

 directions (PI. VII. c, c, c). The nature of the small species is not 

 likely to be disputed: it is certainly a track of some kind, and 

 it is remarkable that it never turns aside as it approaches the 

 large grooved form, but passes over it at once, ploughing its 

 way exactly in the same manner as it has done on the level por- 

 tions of the sandy beach. The furrow is precisely of the same 

 character, form, and depth, whether on the slab or on the track, 

 and the ridge thrown up on each side is in no respect dissimilar. 



