400 Proceedings of the Royal Physical Society. 



in the list) were detected in the boulder clay, which came 

 from the chalk formation ; these, with the great quantity 

 of other chalk material, also in the boulder clay, connected 

 with the abundance of chalk flints which are met with all 

 over the surface of Caithness, as shown in a paper of mine 

 read to the Society some years ago, give room to suspect 

 that in all probability the chalk formation, and that pretty 

 largely developed, as shown by its widespread ruins, was not 

 far distant from Caithness, and it would be well to collect all 

 the evidence possible on this desirable and interesting subject. 



The fragmentary state of the organisms proves that they 

 could not have lived and died where now found, as no two 

 valves were found united (with the exception of two very 

 small Anomias) amongst the hundreds of specimens taken 

 out of the clay. There is no doubt that these minute shells 

 were sheltered in hollows in the rock masses to which they 

 were attached when living, and, when these masses were 

 removed, held fast by their strong plug, and only became 

 loose when this had decayed ; and thus these delicate and 

 frail shells escaped destruction. Mr J. Anderson, of Wick, 

 got a nice group of young Balani, in a pretty good state of 

 preservation, attached to the fragment of a shell. These 

 being such rare instances, I have thought it right to men- 

 tion them. 



Many of the organisms are microscopic, and were washed 

 out of this stubborn clay by myself and Mr J. Anderson, 

 and it is thus that the list has been so greatly extended. 

 The most abundant shells are Cyprina islandica, dstartes, 

 Tellina solidida, Turritella communis ; the latter occur in a 

 pretty perfect state, and from microscopic size to more than 

 two inches in length, and in such abundance that, in three 

 walks up theBurnofHaster,Igot more than eighty specimens, 

 and did not take all I saw. However, it would be well not 

 to think such great riches are always to be had, for at times 

 scarcely any specimens are to be got. A few of the others 

 are pretty frequent, whereas Purpura lapillus, Trochus Zizi- 

 phinus, Patella vulgata, Mytilus edulis, Mya truncata, Litto- 

 rina littorea, Ostrea edulis, and other littoral and shallow- 



