292 Canadian Record of Science. 
the walrus and other animals, and is much used by the in- 
habitants. It also appears that a small variety of W. are- 
naria, with brown epidermis, is most common in Greenland, 
and occurs with Mya truncata, which is, however, more 
plentiful. The description given by Fabricius of MW. arena- 
ria obviously agrees with that of my small and brown 
variety from Metis. 
It is interesting to note the companionship of these allied 
species in the North Atlantic throughout the Pleistocene 
and Modern periods, and their range of varietal forms ap- 
plicable to each, according to the conditions to which they 
they have been exposed, along with their continued specific 
distinctness, and the preference of each for certain kinds of 
environment, so that in some places one, and in others the 
other, predominates, while this relative predominance, as 
well as the prevalence of certain varietal forms, might no 
doubt be reversed by change of climate or of depth. 
On MopERN CONCRETIONS FROM THE St. LAWRENCE. 
By Rev. Pror. Kavanaau, 8. J. 
With REMARKS ON CYLINDERS FOUND IN THE PoTsDAM 
SANDSTONE. 
The modern concretions referred to were collected on the 
the rush-covered shores of the St. Lawrence near Boucher- 
ville, and may be thus described :— 
They resemble small radishes, like these, varying much 
in shape, are symmetrical, perforated axially, the more or 
less perfect bore or perforation often containing vegetable 
fibres. 
Their production seems to be due to the action of the 
rush roots upon the soft, plastic clay, so indurating it that 
it can resist the wash of the waves; the receding of the 
water during the summer leaves these concretions standing 
out in relief, like fossils on a weathered surface. 
