CEPHALOPODA. 
Siphuncle ventral, internal; its characters have not been fully observed. 
Test strong, having a thickness of two mm. over the chamber of habitation 
and larger part of the chambered portion. Surface marked by fine, irregular, 
lamellose lines of growth, and fine, regular, longitudinal strioe. The surface 
of the nacreous layer, as shown by the exfoliation of the epidermal layer, is 
preserved as imbricating, lamellose lines, with obscure longitudinal striae. 
The ventral side is indicated by a broad, decided sinus in the surface-striae. 
The internal mould is characterized by the smooth chamber of habitation, 
the crenulated zone and the longitudinal carina, with traces of the crenula- 
tions extending over the walls of the air-chambers. 
An individual, nearly entire, has a length of 180 mm., of which sixty mm. 
pertain to the chamber of habitation. It preserves about twenty-five air- 
. chambers, and has a diameter of sixty-eight mm. at the point of greatest 
transverse section. Another larger individual, imperfect at the apex, and 
of the same proportions, has a length of 190 mm. 
This species is distinguished by its long, fusiform shape, the position of the 
point of greatest transverse section, and its large aperture. It is not so rapidly 
expanding and gibbous as G. eximium, and is of smaller size. A specimen found 
in the drift in Michigan, and probably coming from the calcareous beds of the 
Hamilton group, in the northern part of the lower peninsula, cannot be distin¬ 
guished from the species as occurring in the Goniatite limestone of the Marcel- 
lus shale. It is associated in New York with G. solidum, but in that species the 
chambered portion is conical and rapidly enlarging, and the point of greatest 
gibbosity is on the chamber of habitation, from which the slope of the sides to 
the aperture is sudden and rapid. In the Goniatite limestone the specimens 
are associated with Goniatites Vanuxemi and Orthoceras Marcellense. 
Formation and localities. In the Goniatite limestone, at Manlius, Onondaga 
county, N. Y.; and in the glacial drift, at Ann Arbor, Mich. 
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