284 



DE. C. A. MATLEY ON THE 



[May 1906, 



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the slates are so arranged, that their long axes lie in the direction of 

 cleavage. Usually they are imperfectly cleaved, and their edges are 



tailed out into thin plates. Several 

 '^/T/k'i^'^^i'^///// adjacent nodules at one spot were 

 found to measure as much as 36, 40, 

 and 63 inches respectively along the 

 cleavage, though none of them ex- 

 ceed 7 inches across the cleavage. 

 They are clearly deformed by the 

 compression, but their length in 

 comparison with their width is so 

 great that it is difficult to regard 

 them as of ordinary concretionary 

 origin. Although it would be rash 

 to dogmatize in the case of such 

 rocks as limestones, in which con- 

 cretionary structure is so common, 

 and is no doubt the origin of many 

 of the nodules at Rush, I am con- 

 vinced that in numerous instances 

 the lumps of limestone lying in the 

 Rush Slates were once portions of 

 bnnds that have been broken up by 

 movement, which has squeezed the 

 soft shale of adjacent beds into the 

 interstices between the separated 

 fragments. A reference to fig. 4 

 shows that a mass of nodules is 

 associated with the limestone-band 

 R4<7, and this the writer regards as 

 a broken-up part of the band lying 

 in a synclinal fold. Other instances 

 occur of thin limestone-bands in 

 the slates, slightly oblique to the 

 cleavage, being converted into a 

 connected string of phacoids elon- 

 gated along the cleavage -planes. 

 In the higher part of the slates, 

 where the dip is high, the lime- 

 stones break up into phacoids which 

 are, however, practically continuous 

 one with the other. 



SQ 



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(b) The Rush Conglomerate- 

 Group (Megastoma-Beds) . 



j These consist of numerous beds of 



very regularly - stratified conglome- 

 rate, occurring singly or several 

 together, and separated by narrow or wide intervals of sandy 

 calcareous flags, sandy and pebbly limestone, and laminated shale. 



