ON THE GEOLOGY OP ST. JOHN. 247 



To the westward of St. John this group thins out rapidly. At 

 the " falls " of the river it does not exceed 150 feet. 



No organic remains have been detected in it. 



St. John Group. — No division of these slates has been at- 

 tempted, as there is a repetition of similar sediments ; the strata 

 are much plicated, and the only well preserved fossil — a lingula — 

 which occurs in considerable number is common to the coarser 

 beds throughout the group. 



The great mass of the deposit consists of a grey clay slate often 

 sandy, the layers of which present glistening surfaces owing to 

 the abundance of minute spangles of mica. This rock frequently 

 becomes very fine in lamination and texture, and dark in colour. 

 Four thick bands of this kind occur, the uppermost of which has 

 been denominated by Dr. Dawson papyraceous shale. They have 

 as yet yielded no fossils* The three bands of coarser shale 

 which alternate with them include numerous layers of a fine com- 

 pact grey sandstone, from a few inches to ten feet or more in 

 thickness ; a few are so highly calcarerous as to become almost 

 limestones. The surfaces of the layers in the coarser bands are 

 frequently covered with worm burrows, ripple marks, shrinkage 

 cracks, scratches — apparently made by creatures gliding through 

 the shallow waters in which they were deposited — and other evi- 

 dences indicating that the slates are in great part of littoral origin. 



Fragments and complete shells of a Lingula are scattered 

 over the surfaces of the sandy layers, and thin seams composed 

 entirely of these shells packed closely together are occasionally 

 met with. 



These shales maintain a comparatively uniform breadth between 

 Loch Lomond and St. John, but to the westward of the city their 

 thickness rapidly diminishes. No proof that they are unconform- 

 able to the deposits contiguous to their base and summit has been 

 observed. 



* Since writing the above, I visited, in company with my brother, Mr. 

 C. R. Matthew, a locality on Goldbrook where he had previously met 

 with loose pieces of fossiliferous slate. We found this rock in place 

 near the base of the St. John group, and obtained from it, beside some 

 obscure remains, a small orthoceratite, and numerous trilobites of two 

 or three species, the latter so excessively distorted that not even the 

 genera can be made out. These and the species discovered in the Da- 

 doxylon sandstone by Mr. Payne, are, I believe, the only trilobites found 

 in situ in the province. 



