2<)i> The American Geologist. October, 18M 
much smaller and more circular in cross-section. Thus toward 
the upper extremity of the shell a cylindrical tube is formed. 
Upon comparing the bodies as thus described with the single 
specimen which represents more nearly the structure of the 
entire shell, it appears that the orientation above assumed is 
not strictly correct. The normal position of the conical pos- 
terior portion is such that the straight and the oblique side 
converge at nearly the same angle to the vertical axis ; this di- 
verts the cylindrical or upper portion of the body to one side. 
These peculiar bodies are siphonesjthose represented on plate 
VI, figs. 2 and 3, show the oblique impressions left by the septa 
upon the surface of the cylindrical portion, and fig. 1 affords a 
conception of the relation of these si phones to the septate part 
of the shell. In the latter is seen the central and symmetrical 
position of the apical cone with reference to the entire shell. 
it> abrupt contraction and the deflection of the cylindrical 
part of the sipho to one side. At the point where the con- 
traction of the sipho begins, its diameter is that of the shell. 
and from the apex to this point there is no trace of septa. 
With the appearance of the septa begins the contraction of 
the sipho. That the septa did not completely encircle the 
sipho is shown by several of the specimens which present a 
smooth surface on the dorsal or outer side, the marks of the 
septa being there interrupted (figs. 2, 3). One of the speci- 
mens has the thin wall of the conch adhering to the siphonal 
wall along this surface. 
Upon examination of the internal structure of these si phones 
they are found to be completely solid in the apical portion for 
usually about one-half the length of the pneseptal cone, but in 
some examples this solidification extends for the entire length 
of the cone and into the cylindrical part of the tube. The 
cavity of the sipho above this filling is a narrowly conical 
chamber whose walls gradually become thinner from the apex 
upward, their upper edge appearing to be rounded off and fin- 
ished. 
The substance of the siphonal cone and walls is invaria- 
bly very compact, radially crystalline calcite. indicating, inas- 
much as all the specimens have been found in calcareous 
shales and clayey limestones, a simple modification of the 
