41 
Leray and in the lower beds of the Trenton a transition zone, 
during which period the life of the Black River sea gradually 
gave way to the life of the Trenton sea. This transition fauna is 
given in detail in the following tables. The same gradation is 
evident in the lithology; the fine-grained grey limestone of the 
Black River grades into the dove-tinted, coarser limestone of the 
Trenton beds. In the Ottawa section the lowest exposed beds 
of the Trenton and the top of the Leray beds are separated by 
a field concealing the contact. The former are tilted much more 
than those above or below, probably the result of a small fault. 
A small, abandoned quarry to the east of the road shows in one 
small area the line of a local fault. As remarked above, the inter- 
bedding of shale both in the Black River and Trenton, forms a 
less evident feature than at Rockland, and where it is present in 
some of the Trenton beds, the shales, unlike those at Rockland, 
are almost unfossiliferous. The lithology shows the same change 
as at Rockland, but on account of the lack of continuity in the 
exposures the gradations are not so evident. The fossil content 
also exhibits in the same way the evidence of a transitional 
period at the close of the Black River and the opening of the 
Trenton era. 
The close relationship of the Trenton and Black River 
faunas is shown in the following table: 
Comparison of faunas in Trenton and Black River 
Leray 
Rock- 
land 
Spongtse 
Hindia parva Ulrich 
c 
r 
Incertse Sedis 
Receptaculites occidentalis Salter 
r 
c 
Anthozoa 
Columnaria halli Nicholson 
c 
- 
Streptelasma sp 
- 
r 
5. corniculum Hall 
rr 
cc 
S. profundum (Conrad) 
cc 
rr 
Tetr odium fibratum Safford 
cc 
c 
Stromatoporoidia 
Stromatopora sp 
- 
r 
Stromatocerium rugosum Hall 
c 
- 
