190 



ON SOME TRAILS AND HOLES FOUND IK KOOKS 



general character some of them are not unlike the trails made 

 l)y natica or littorina, and others are more like the mean- 

 dering trails of idotea^ In many the great length of the 

 meandering line, which crosses and recrosses itself in many 

 times, seems to indicate that the animal moved rapidly over 

 the surface; in others the trails are larger, and the animal 

 probably moved much more slowly, the length being often 

 limited to a few inches. These trails vary greatly in size — 

 from a diameter of half a line to half an inch, — and the 

 smaller ones as a general rule are the longest, and shew more 

 recrossings than the larger ones." 



In the specimens from Hutton Roof no evidence of the 

 annelid or mollusc is found, and the trails are the only re- 

 mains left of the creatures which made them. Doubtless at 

 the time of the deposition of the beds now forming the flags, 

 both these departments of the animal kingdom existed, if we 

 may judge from the organic remains in strata found both above 

 and below those in which the fossils were met with ; and the 

 inhabitants of the huccinum gihsoni and other shells found 

 in the limestone shale, could have made a trail of about the 

 same size as those of the specimens. From the meandering 

 character of the trail, crossing itself several times like that of 

 the littorea littoralis, it bears more evidence of having been 

 made by a mollusc than an annelid. The bottom, too, of 

 the trail is flatter, and not so concave as that of a worm 

 generally is. This also appears to have been the opinion 

 of Professor Hall, with regard to the American specimens 

 before alluded to. 



In my cabinet is a slab of flagstone from a quarry belonging 

 to Mr. Jonathan Whitaker, at Dyke Nook, between Hebden 

 Bridge and Keighley. The stone is much used for making 

 grindstones. Its upper surface is thickly covered with mean- 

 dering trails in relief, similar to the smaller ones before 

 described at Hutton Roof, except that they are about four 

 times the size of those specimens, and do not cross each other 



