122 A. H. Foord—Ascoceras Murchisoni, Barr. 
shows distinctly two air-chambers of very unequal height, and 
bounded by three superposed septa, in the following order :— 
“1. Terminal septum of the body-chamber, as seen in other 
~examples of Ascoceras. 
«2. Septum placed below the preceding, at a distance of about 
7 mm. from the body-chamber. A like distance has never been 
observed in any other specimen in which two septa could be recognized 
below the body-chamber. 
“3. Terminal septum, situated about 2 mm. below the preceding 
one, and constituting the abrupt truncation characteristic of the 
posterior extremity of Ascoceras. 
“This truncated end is very distinct and has a smooth surface. 
The edge of the test is seen around its external border, and from 
Fig. 1. Lateral view of Ascoceras Murchisoni, Barr., showing the body-chamber 
nearly complete, excepting the margin of the aperture. The lower part 
presents a longitudinal section, showing three very unequally spaced septa, 
abruptly truncated below. 
Fig. 2. Transverse section of the same specimen, following the line a—d (Fig. 1). 
Fig. 3. Lower extremity of the same specimen, enlarged twice, to show more 
clearly the three septa. 
Fig. 4. Surface of terminal septum (pan coupé) of the same specimen ; bordered by 
the edge of the test, which is here broken by natural truncation.! 
Fig. 5. Ascoceras, after Lindstrém. 
1 Fig 7 of Barrande’s plate, an enlargement of the ornaments of the test, is 
omitted, as unnecessary for the present purpose. 
this border the test spreads over the external surface of the fossil, 
and exhibits the ornamentation characteristic of this species, con- 
sisting of a net-work of fine striae. 
“The phenomena just described clearly prove that, in Ascoceras, 
