298 
IOWA ACADEMY OF SCIENCE 
mum diameters of the segments are in proportion of approxi- 
mately thirteen to nine while the height to the width is about 
three to five. Two segments meet along a slightly oblique plane. 
The endosiphuncle is central and small. The lamellae are few 
and rather obscure in our specimen. 
Fragments of the septa preserved with this bit of siphuncle 
indicate that the septum on emerging from the septal groove 
turned abruptly upward and adhered to the lower half of the 
segment; from this position it defiected outward to unite with 
the conch. The smoothness of the lower half of each segment 
seems to be due to the fact that it was covered and thus protected 
from weather and wear for some time after the destruction of 
the enveloping conch. It is worthy of note that the lower half 
of the segments in M. ohliqua also is smoother and strongly sug- 
gests, in our material, a similar relation of septa and siphuncle in 
that species. 
Measurements : Greatest diameter, three successive segments, 
27.0, 26.0, 25.8 mm.; least diameter, three successive segments, 
18.5, 18.0, 17.2 mm. ; average length, three segments, 14.5 mm. ; 
obliquity, 95°. 
Occurrence and Locality: The only specimen in the Univer- 
sity collection is from the Niagaran, ‘‘northeastern Iowa.” 
Discosorus (?) bieonoideus sp. nov. 
Plate XXXIV, figures 1 and 2. 
Compare Discosorus conoideus Hall, 1852. Pal. N. Y., Vol. ii, p. 99, PI. 
xxviii, figs. 13a, b, c. 
Siphuncle of the nummuloidal type, straight, transverse sec- 
tion circular; tapers both posteriorly and anteriorly giving the 
specimen a biconoid appearance. The anterior cone is the 
shorter due to more rapid tapering in this direction. 
Segments disc-like, edges rounded, septal groove deep, oppos- 
ing faces flat and smooth ; anteriorly the segments become thinner 
at the extreme end showing that the air chambers in senility be- 
come shallower. The obliquity of the plane passing between the 
joints is as high as 105° which is greater than in any species of 
Huronia. 
Endosiphuncle central ; internal character of the segments ob- 
scure but where broken small fragments of crinoid or cystoid 
stems and hollow molds of minute fossils tend to indicate that 
