368 J. W. Dawson on fossils from the Laurentian of Canada. 
part of the length. Above this is an abrupt projection, and then 
a sudden narrowing; and in the middle of the narrow portion, 
a part has the chambers obliterated by a white patch of carbon- 
ate of lime, below which some of the septa are bent downward 
in the middle. This is probably an effect of mechanical injury, 
or of the interference of a cale-spar vein. 
With the exception of the upper part above referred to, the 
lateral orifices opening into the chambers. It is worthy of 
remark that, in this respect, the present specimen corresponds 
exactly with that which was originally figured by Sir W. Logan 
in the ‘Geology of Canada,’ p. 49, and which is the only other 
Specimen that exhibited the lateral limit of the form. 
On the side next the matrix, the septa terminate in blunt edges, 
and do not coalesce; as if the organism had been attached by 
that surface, or had been broken before. being im 
power, the margins of the — appear uneven, as if eroded or 
e of growth; but occasionally the 
septa show a distinct and regular margin. For the most part 
merely traces of structure are presented, consisting of small parts 
of canals, filled with the dark coloring-matter of the limestone. 
In a few places, however, these appear as distinct bundles, sim! 
characteristic of the proper chamber-wall of Eozoon, For the 
most part this seems to have been obliterated by the infiltration 
of the tubuli with colorless carbonate of lime, similar to that 0 
the skeleton, 
In comparing the structure of this specimen with that of those 
found elsewhere, it would appear that the chambers are more CoB- 
ee In the two former respects the specimens from the Calu- 
isms ; and, so ar as can be ascertained, this may have 
same in the present specimen and in that originally obtained from 
ae ‘alamet, while in specimens from net le a massive 
i Bnd | | 
vidual shape. Without additional | 
SRE eae gee 
il 
ve mode of le seems to have obliterated all 
Wee ee ss Oe 
