No. 5.] PAISLEY — ON THE POST-PLIOCENE. 26f^ 



to the rocks of the neiuhbourini^ formations; but some have 

 their representatives in KestiLiouche, near Dalhousie. 



The surf ice of this formation, wliich seldom attains a irreater 

 elevation than about 150 feet, is marked bj a g:ood deal of 

 inequality. 



The Leda clay is generally, when wet, of a reddish hue^. 

 dryinp^ into a darker but less decided tint, and may possibly 

 have been derived, in part, from the red Sub-carboniferous rocks 

 in the neighbourhood. It varies a great deal in thickness, and. 

 through it there are distributed thin layers of sand that main- 

 tain a uniform thickness, shewing that they must have been de- 

 posited in a gently moving current, or in some quiet and pro- 

 tected place. Indeed all through the middle and lower part of 

 this bed the fossils are so well preserved and so little mutilated, 

 that they must have been depo.;ited very gently. JVticuIa, which, 

 is quite abundant, is extremely well preserved with the valves, 

 united, epidermis fresh looking and perfect, and the teeth whole. 

 Ml/a also is well preserved, retaining quite frequently the epi- 

 dermis, and, in this respect, contrasts with specimens found in 

 the fossiliferous bed constituting the lower part of the Saxicava* 

 sand and the upper part of the Leda clay. I have once or twice 

 found what would seem to be cracks or holes 2 — 3 feet deep ia 

 this bed almost filled with JVacula tenuis and N. expansa, with 

 an occasional Cryptodon, A^atica, Macoma, and Balaams. So 

 abundant were the jN'HCuIm that a pint might be readily washed 

 out of a shovel full of the clay, which was much blackened by 

 the decomposition of animal matter. What was the origin of 

 these holes and why they should be filled so abundantly with 

 Huculce to the almost entire exclusion of other shells, I cannot 

 conjecture. 



The Saxicava sand is also very irregular as to thickness, and 

 terminates, in most places, abruptly on the uneven surface of 

 the Leda clay. It would seem that before the deposition of the 

 sand, currents or some other agents grooved and hollowed out 

 the underlying clay, and that these irregularities were filled up 

 bj the sand, which seems to have been deposited by somewhat 

 violent currents in unquiet waters. More rarely, however, in- 

 stead of the one formation passing abruptly into the other, they 

 gradually merge, so that it cannot be said where the one ends 

 V lid the other begins. The surface of the Saxicava sand is even 

 more irregular than that of the Leda clay, either from the in- 



