'Calvin on the Hamilton in Ontario. 8i 
merely as an incentive to future investigation and pointing in 
the direction which it ought to take. Before the views above 
presented can be definitely established, thei^e must be further 
investigations, first, on the relation of the island flora to that of 
the mainland ; second, on the relation of the flora of California 
to that of adjacent parts from which it may have been origi- 
nally colonized; third, and especially, must we have fuller 
knowledge of the indigenous flora of California in Pliocene 
times. \^BiiUetin No, 8., California Academy of Sciences. '\ 
OBSERVATIONS ON THE VERTICAL RANGE OF CER- 
TAIN SPECIES OF FOSSILS OF THE HAMILTON 
PERIOD, IN WESTERN ONTARIO. 
BY PROFESSOR S. CALVIN. 
The region about Widder, Arkona and Bartlett's Mills in 
Lambton county, Ontario, has long been classic ground to palae- 
ontologists. Clay shales of the Hamilton period are found in 
natural exposures along the bluffs bordering the Aux Sables 
river and its tributary creeks near Arkona and Bartlett's Mills. 
A portion of the same shales has been exposed by the railroad 
cutting, three quarters of a mile east of Widder. The profu- 
sion of fossils of the period occurring in these shales is something 
remarkable; and the perfect state of preservation in which the 
fossils are found renders them exceedingly attractive to students 
of palaeontology. 
The geological section accessible to observation in the region 
referred to is probably not more than 200 or 250 feet in thick- 
ness altogether. Nevertheless the section is naturally divided 
into three distinct portions, each sharply set off from the others, 
not by lithological, but by palceontological characteristics. So 
marked and so distinct are the groups of species characterizing 
the three separate portions of the section that it is scarcely an 
exaggeration to say that not a single species is common to any 
two of them. 
No attempt will be made in the present paper to enumerate 
all the species belonging to the three distinct assemblages of 
