MINERALS AND GEOLOGY OF CANADA. 21 
the vertebral column of a fish. Weathered specimens of this kind are 
usually described by quarrymen and farmers as fish remains ; but no 
vestiges of a true fish, or other vetebrated type, have as yet been dis- 
covered in our Silurian strata. 
In the third sub-genus, for which, without regard to the supposi- 
tion originally involved in the term, Prof. Hall’s name of Lndoceras 
may be retained, we may place the orthoceratites with very large and 
laterally-situated or more or less marginal siphuncle. ndoceras 
proteiforme, of Hall, (fig. 
131), is a familiar Cana- 
dian example. The si- 
phuncle, in this species, 
often contains a long cone 
of calcareous matter, made 
up of successive layers. 
This secretion probably 
served to counterbalance 
the increasing buoyancy of 
the shell, as the air-cham- 
bers during the growth of 
the latter became more 
and more numerous. The 
shells of smaller orthocer- 
atites are also sometimes 
found, with other acciden- 
tal bodies, in the interior 
of these large siphuncles. 
Examples of Kzdoceras 
proteiforme, five or six in- Fig. 131. 
ches in diameter, and in fragments of over eighteen inches or two 
feet in length, have been obtained from the Trenton limestone of 
Nottawasaga township, near Collingwood, C. W.; also from Belle- 
ville ; and from the Hudson River beds of the River Humber, near 
Toronto, as well as from other parts of the Province. One of the 
largest specimens, yet collected, was obtained by the writer from the 
shores of Georgian Bay, (Lake Huron,) and is now in the Museum 
of the Toronto University. 
Note :—We have retained for the orthoceratites described above, the specific 
names by which they are familiarly known in Canada, after the determinations 
of Prof. Hall in his “‘ Paleontology of New York.” But Orthoceras lamellosum 
