2 
MUSEUM BULLETIN NO. 20. 
are about 70 feet thick, consist of thin to thick-bedded dolomite 
with interbedded shale, and contain numerous Niagara fossils. 
Except in the vicinity of Hamilton and Guelph, the Eramosa 
beds appear to be unfossiliferous. 
The Guelph formation rests conformably upon the Eramosa 
dolomites, the contact being transitional and the lower Guelph 
beds being quite bituminous at many of the southern localities. 
The Guelph beds are, however, usually 1 to 2 feet thick. 
Where well exposed, the Eramosa beds exhibit beautifully 
symmetrical domes 100 to 200 feet across with centres rising 
15 to 20 feet above the rim. Along the north shore of the Bruce 
peninsula such domes are common. In the eastern part of the 
city of Guelph, a well developed dome has been left in the floor 
of a quarry. This is at the top of the Eramosa beds. South 
of the prison farm near the Eramosa river, a coral reef rises 
through Eramosa beds which have been eroded from its top 
but still flank its sides. The reef is 35 yards wide by 85 yards 
long and rises about 20 feet at the centre. Some irregular 
bedding shows at one end. The following fossils were found in 
the reef material: Stromatoporoids , Ompkyma stockesi Edwards 
and Haime, Pycnostylus guelphensis Whiteaves, P. elegans 
Whiteaves, Favosites hisingeri Edwards and Haime, Cladopora 
sp., Heliolites spinopora Hall? Bryosoa , Rhynchotreta cuneata 
americana Hall ?, Camarotoeckia neglecta (Hall), and a trilobite 
pygidium. 
This fauna is in the main typically Lockport, but the pres- 
ence of the two species of Pycnostylus, which are among the most 
typical of Guelph species, indicates that in this old reef tran- 
sitional conditions existed. The reef explains the origin of one 
mound which formerly existed in the Eramosa beds. 
LOCATION AND OCCURRENCE OF THE EURYPTERID 
FAUNA. 
East of Guelph at the crossing of the Canadian Pacific 
and Canadian Northern tracks and not far south of the Eramosa 
river, the Canadian Northern road bed has been constructed 
of chocolate brown, bituminous shales excavated from the right 
of way. It is these shales that furnished the fauna here described. 
