4G GEOLOGY OF ARRAN. 



published in the Transactions of the Society, vol. xxiii. part 3, 

 p. 523. Soon after we visited the chief locality, which is on 

 Torlin Water, about one mile inland, and twenty or thirty feet 

 above the stream, and found seven of the species, in an hour's 

 digging, besides two species of foramenifera not in the list. 

 The following is a list of the shells : 



Balanus crenatus. 



Purpura Norvegica. 



Tellina Baltica, a brackish- water variety of solid ula. 



Cyprina Islandica. 



Astarte elliptica. 



arctica. 



compressa. 



striata, a very large variety of compressa. 



Cryptodon Sarsii. 



Modiola modiolus. 



Leda pygmsea. 



pern ula. 



Pecten Islandicus. 



opercularis. 



Littorina littorea. 



Turritella communis. 



Natica ? 



The perfect state of preservation of most of the shells indi- 

 cates a quiet deposit on the sea bottom ; the elevation of the 

 bed above the present sea-level expresses the amount of 

 former depression below that level ; it expresses, indeed, a 

 much greater depression, since many of the shells are exclu- 

 sively deep-water species : the Cyprina Islandica, for ex- 

 ample, is not met with in our seas higher than at a depth of 

 ten fathoms. Further, it follows from what has been stated 

 in regard to the relative position of the beds, that if we can 

 trace an undoubted boulder-clay deposit up the glens to the 

 height of 1000 or 1500 feet, even if we find no shells, the 

 elevation unquestionably indicates this amount at least of 

 former depression. 



