242 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 5, 



in the state of fine lines emanating from several centres, and joining 

 together in the usual manner of cracks in sun-dried mud. 



The features which mark this occurrence, and also the laminae in 

 which it is seen, distinctly point out the deposition of mud in a lo- 

 cality where littoral conditions prevailed ; and where the subsequent 

 exposure of this fine mud to solar influence caused it to shrink : these 

 very ancient desiccation-cracks afford us the earliest direct evidence 

 which we possess of land above the surface of the waters of the 

 palaeozoic sea. 



In the deposits which occur at Binks, and also in similar beds on 

 the north side of the axis in the Tinwald range of hills, there are 

 found pitted hollow markings on the surfaces of the strata ; and, on 

 splitting one of the thin beds in which these markings are seen, the 

 latter are found frequently to extend through the thickness of the 

 stratum. At first sight they appear to have been formed by marine 

 worms in their burrowings ; but, as they decrease both in diameter 

 and distinctness as we proceed downwards, they could not have re- 

 sulted from such a cause. On examining the base of a stratum where 

 these markings are seen, they are found to occur in the form of 

 small, somewhat circular hollows, all tailing away in one direction. 



These markings, from their nature and the mode of their occur- 

 rence, seem to have arisen from the influence of very slight currents, 

 which, meeting with some small impediment, probably in the form of a 

 grain of sand, washed a small hollow in the side offered to the flow of 

 the water ; and during the deposition of the mud forming the strata 

 these hollows contiimed to increase in size, until they assumed some- 

 what of the form of the burrows of Annelids. 



In these low strata we possess proofs of currents in the form of 

 ripple-markings, also in the gentle drifting of the mud which consti- 

 tutes these beds ; and the lithological nature of the deposits indicates 

 that they have had their origin in shoaling water ; and, even at this 

 remote geological time, we see evidence of a muddy shore in the 

 presence of the sun-cracks which fissure the laminae of the fine shales 

 of these beds, belonging to a series of strata which are among the 

 most ancient of the palaeozoic division of sedimentary deposits. 



Nor are these beds altogether devoid of such evidence as shows 

 the existence of animal life during the period when they were being 

 formed. At the locality already alluded to as affording distinct 

 proofs of the operation of causes such as now prevail in shallow 

 water, we find the surfaces of some of the strata marked by the 

 meandering tracks of Annelids ; showing the existence of this form 

 of animal life in this locality at a very early period. These annelid- 

 tracks are not, however, the only circumstances which indicate the 

 occurrence of animal life ; for we have a track also of another kind, 

 and such as seems to have had its origin in the wanderings of an- 

 other tribe of animals, viz. Crustaceans. This track consists of a 

 central line and two lateral series of markings (see fig. 2) . The cen- 

 tral line appears to have been formed by either a keel-like projection 

 on the lower portion of the animal, or to have originated from the 



