The Canadian journal of industry, science and art . Fif?. Represents the aperture. Fig. 134, To this genus, Halls Oncoceras constrictum (fig, 134) should alsobe referred. This species is exceedingly common in the low part ofthe Trenton group ; but when in imperfectly preserved specimens, itcannot be distinguished from a cyrtoceras. The siphuncle is near theoutside or larger curve of the shell. Lituites:—The shell in this genus, is involute or rolled u(like that of the nautilus) for a certain distance, and is then pro-jected in a straight line. The septa are simply concave, and thesiphun
The Canadian journal of industry, science and art . Fif?. Represents the aperture. Fig. 134, To this genus, Halls Oncoceras constrictum (fig, 134) should alsobe referred. This species is exceedingly common in the low part ofthe Trenton group ; but when in imperfectly preserved specimens, itcannot be distinguished from a cyrtoceras. The siphuncle is near theoutside or larger curve of the shell. Lituites:—The shell in this genus, is involute or rolled u(like that of the nautilus) for a certain distance, and is then pro-jected in a straight line. The septa are simply concave, and thesiphuncle of small size and mostly central. Species have not beenfound as yet above the Silurian rocks. In fragmentary specimens,however, it is often impossible to deter-mine the genus—the straight part of theshell resembling that of an orthoceraswith narrow siphuncle, and the involuteportion being identical with the shellof a nautilus. Fig. 135 represents theLituites undatus of Hall. Exampleshaving a general resemblance to this,but (as first pointe
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