216 ON THE TWO SPECIES OF 
Amongst these, the most characteristic is the Megalomus Canadensis, 
usually found in the form of internal casts, as shewn in fig. 224.* 
As a general rule, the fossils in these beds are somewhat obscure, 
and not very abundant. The principal exposures of the formation 
occur on the River Speed in the vicinity of Guelph ; at Elora, on the 
Irwine and Grand River, where it presents vertical cliffs over eighty 
feet in height ; at Hespeler on a branch of the Great Western Rail- 
way, ; and lower down the Grand River, at Preston, Galt, and places 
in the township of Dumfries. At present, the Guelph formation can 
only be regarded as a provisional group, its strata appearing more or 
less to merge into the underlying Niagara beds, and in some locali- 
ties, also, to offer a passage into the Onondaga deposits. 
(To be Continued. ) 
ON THE TWO SPECIES OF ASTACUS FOUND IN 
UPPER CANADA. 
BY T. J. COTTLE, ESQ. 
Read before the Canadian Institute, April, 1863. 
Of the fresh water Lobsters as restricted by M. Milne Edwards to 
the genus Astacus, that learned historian of the Crustacea, in his valu- 
able monograph enumerates but five. Of these he gives one to Europe, 
two to the North East side of America, one to Chili, and one to Aus- 
tralia: since his book was published one has been added to the North 
West of this continent, under the name of Oreganus; and it is my 
intention to bring before the consideration of the Canadian Institute 
another, which I think, will form a new species indigenous to this 
Province, and which I propose naming (fodiens) as being appropriate 
to its habits. It is possible that it may have been already described, 
for the want of a good library of reference is a great impediment to 
the discrimination of species. I therefore feel a degree of diffidence 
in naming it. 
The species described in the Natural History of the State of New 
York, as the only one belonging to it, is the Astacus Bartonii, and I 
* This fossil is described in Part IV. as occurring in the Onondaga Group, the Guelph 
strata having been originally referred to that subdivision. 
