56 POST-TERTIARY ENTOMOSTRACA. 



Cytherura similis, G. O. Sars. 



— undata, G. O. Sars. 



— Sarsii, Brady. 

 Cytheropteron latissimum (Norman). 



14. Kyles of Bute. 



1. Tiyh-na-bruaich. — Walking along the shore, and proceeding from high-tide-mark 

 to low, the following series of beds is passed over : 



(1.) Boulder Clay, hard, compact, unfossiliferous. It is red in colour through the 

 ferruginous character of the mica-schist of which the included boulders largely consist, 

 and which constitutes the base rock on which it rests. 



(2.) Laminated clay, remarkable for the decisiveness and freedom of its laminations 

 and of the same character as that described in other beds. 



(3.) Shell-clay, rich in characteristic Arctic shells. This bed is composed of clay and 

 sand mixed in various proportions at different points. At some points a pure sand, at 

 others a pure clay, is found, and there are all possible intermediate varieties. 



To the left of the pier, covered with one to two feet of sand, is an extensive bed of 

 Pecten Islandicus, the shells having both valves united, and being in their natural 

 position. 



Saxicava {Panopcea) Norvegica with Mya truncata, var. Uddevallensis, also occur in a 

 thick clay, adjoining the sand, of large size, standing in their natural boring position. 

 Astarte compressa and A. sulcata can be picked out from the clay also with united valves, 

 and large valves of A. borealis may also be found. 



To some of the boulders imbedded in the clay large specimens of Balanus porcatus 

 are attached. 



The true order of these beds is the reverse of the order in which they are passed over 

 in walking from high- to low-tide- mark. The action of the sea has swept away the 

 upper parts of the beds ; and since the denudation has been most complete where the 

 waves have broken upon the shore, the lowest bed (the Boulder Clay) is the most exposed 

 at that point ; the middle bed (the laminated clay) is still less exposed ; and the upper bed 

 (the shell-clay) is the least exposed of the whole series. This order is invariable through 

 the whole length of the Kyles, although one or other of the beds is occasionally absent. 

 Eossils might appear at first sight to be in the Boulder Clay when they really occur at 

 points where the fossiliferous bed is in immediate contact with it, the laminated clay 

 being absent. 



On the Bute shore, immediately opposite Tigh-na-bruaich, the same beds are visible 



