278 Cincinnati Society of Natural History. 
With the exception of a small portion on the north shore, between 
Cape Rouge and Quebec, and part of the island of Orleans, itis en- 
tirely confined to the south side of the St. Lawrence ; where its north- 
western limit occurs between Missisquoi Bay and Cape Rouge; and 
southeastern limit is traced from Stanstead, east of Lake Massawippi, 
to St. Francis river, and along this river to Lake St. Francis. From 
this the southern boundary is traced to Vandreuil, on the Chaudiere ; 
thence to the northern part of Lake Temisconata, and following the 
province line to Lake Metis. It then stretches eastward to the ex- 
remity of the continent at Cape Rosier. It reaches its greatest breadth 
on the Chaudiere, which is about sixty miles. It forms the continua- 
tion of the Green Mountains of Vermont, and includes in Canada the 
Shickshock and Notre Dame Mountains, and has a thickness estimated 
at more than 12,000 feet. Part of it may belong to the upper part of 
the Calciferous, and another part to the Chazy, but it is exposed only 
in a region much disturbed by volcanic action, and how much if any 
of it is synchronous with other groups may never be known. 
The Chazy, when found superimposed upon the Calciferous, is al- 
ways uncomformable, but when the Quebec intervenes, the connection 
is shown by the gradual change in the fossils from the Potsdam and 
Calciferous below to the Chazy and Trenton above. 
The genera, so far as known, that make their first appearance in this 
group, are distributed as follows : 
Among the Protista, Zrachyum is peculiar to it. 
Among the Polypi, Callograptus and Ptilograptus, recur in the 
Niagara; Thamnograptus in the Hudson River and Niagara ; Dictyo- 
nema in the Trenton, Niagara and Hamilton Groups ; Graptolithus 
and Retiolites in the Clinton ;'Climacograptus, Diplograptus and 
Retiograptus, in the Trenton, Utica Slate and Hudson River; while 
Cladograptus, Dawsonia, Didymograptus, Discophyllum, Monograp- 
tus, Nemagraptus, Nereograptus, Phyllograptus, Staurograptus, and 
Tetragraptus, are peculiar to it. 
Among the Echinodermata, Stenaster occurs in the Trenton and 
Hudson River ; and Palewocystites in the Chazy. 
Among the Brachiopoda, Strophomena occurs in every succeeding 
group to the Devonian ; Stricklandinia in the Clinton and Niagara ; 
and Porambonites in the Black River Group. 
Among the Gasteropoda, Cyrtolites and Metoptoma occur as high | 
as the Carboniferous ; Cyclonema, as high as the Devonian; Fusis- 
pira, in the Trenton, Utica Slate, and Hudson River; and Clisospira 
and Ecculiomphalus in the Trenton. 
