230 J. W. Salter on Fossils from the Ottawa River. 
For instance, one of the most abundant fossils is a species of 
Scalites (Euomphalus uniangulatus), described as a fossil of the 
calciferous sand-rock by Hall. The corals, again, Stromatocerium 
rugosum, Columnaria alveolata, which are very abundant, are 
those of the Bird’s-eye and Black River limestones. 'The former . 
to which I propose giving the name of its discoverer. It is well 
distinguished from M. magna, by the much more rapid increase 
in diameter of its whorls and its minute umbilicus. It is possessed, 
moreover, of a most peculiar operculum, which will at once estab- 
lish the right of Maclurea to rank as a distinct genus, being fur- 
nished within with a broad and strong bony process for the mus- 
cular attachment, and being itself very strong and massive. Prof. 
orbes has undertaken to compare this peculiar operculum with 
that of some rare living gasteropods of far inferior size, so that 
- more need not be said of it at present. 
he Stromatocerium affects also a small and new species of 
Scalites allied to the one above mentioned, and frequently covers 
all but the mouth, so as to mask the form of the shell completely. 
But it is with the Trenton limestone that the greater number 
of species agrees; and while a large portion of them, especially 
the gasteropods, appear to be undescribed in Hall’s work, still the 
analogies are very evident. A list of ten or more Murchisoni@ 
or Pleurotomaria affords one, M. ventricosa, characteristic of the 
Bird’s-eye limestone; two common in the Trenton limestone, 
M. bicincta and M. gracilis (very abundant species), and M. bel- 
licincta, Hall, a large Turritella-like form; the rest seem to be 
new; and some of them are remarkable for the tendency of the 
whorls to separate and become what may be called vagrant, as 
happens in some accidental varieties of the common snail. 
shells are tolerably thick and strong. 
Some smooth shells, exactly like the Euomphalt of the cat- 
boniferous limestone, and several roughly sculptured Turbines oF 
shells of apparently allied genera, occur; and one exceedingly 
elegant, with close thread-like lines of growth, is very common: 
Holopea of Hall, an ill-defined genus, offers one or two species of 
the typical form, and one closely allied to H. biliz of the Wester? 
States. There are three species of Scalites, a genus with t 
mouth notched like Plewrotomaria, but destitute of a spiral bane; 
one is the small species so commonly encrusted over; & sect 
of which we have but a single specimen, is muricated with sp 
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