Annelid Tracks in the County of Clare. 281 



ence that they have sprung from somewhat different circum- 

 stances. When these flags are divided along the laminse of 

 bedding, the lower surface often presents the aspect usually 

 afforded by the higher natural surfaces of these dark-coloured 

 flags, having the sinuous line, with traces of the ventral arch. 

 The surfaces of these sinuous lines, as they are exposed by the 

 cleaving of the flags, are in general much finer, and we com- 

 monly find that they are filled with the substance of the stone, 

 appearing in the form of a thick worm, a transverse section of 

 which has a particular shape, and on applying the split sur- 

 faces to each other, it can be seen that these apparent track s 

 are really the burrows of the annelids in the stone, when it was 

 originally mud, and not tracks on the surface of the sea-bot- 

 tom. These ancient burrows bear every evidence of having 

 been lined with mucus, as are the recent burrows of this tribe 

 of animals ; and into these burrows the mud has flowed, filling 

 them up, and now furnishing the worm-like bodies which are 

 exposed on the split surfaces of the flags. 



These worm-shaped bodies give to us the shape of the bur- 

 row, which was meandering, and flattened perpendicularly. 



There is another circumstance which the surfaces of the 

 higher greenish-gray flaggy strata sometimes presents, which 

 consists of a small funnel-shaped cavity, forming the entrances 

 into these burrows. 



The various appearances of the tracks, and the nature of 

 the strata with which these are associated, furnish some im- 

 portant information concerning the conditions which obtained 

 when this portion of the millstone grit series was being depo- 

 sited. With regard to the tracks themselves, these, from their 

 various states of perfection, indicate that, in some instances, 

 the mud which now constitutes these flags had been in different 

 states, as concerns consolidation, at the time when it was tra- 

 versed by these animals. It sometimes appears to have been 

 in a state so saturated with water that it assumed a pasty 

 condition, partly flowing in upon the tracks after these had im- 

 pressed its surface, and obliterating the markings of the cirri. 

 At other times it seems to have been sufficiently consolidated 

 to afford the requisite conditions for more perfect tracks, as in 

 the case of the higher greenish-gray flags. But even here, we 



