40 Trans. Acad. Sci. of St. Louis. 
occur rarely here. A species identified as Liospira micula 
which has not been recognized below the Utica in the 
Minnesota region is abundant in this fauna and Liospira 
progone which is not reported from below the Trenton 
in Minnesota is represented by several specimens. From 
the evidence furnished by this fauna the beds containing 
it may be safely considered as pre-Trenton in age, but it 
is not entirely clear whether they should be correlated 
with the Black River or the Stones River. 
DESCRIPTION OF SPECIES. 
CTENODONTA AUBURNENSIS, N. Sp. 
Pl., vii. f., 2-4. : 
Shell small, four to seven millimeters in length, three to 
five millimeters in height, length behind umbones slightly 
greater than in front. Umbones prominent, beaks curved 
inward and directed forward. Base regularly convex or 
slightly flattened in the middle, antero-cardinal outline 
slightly concave, posterior umbonal ridge straight to 
slightly convex. Surface of shell marked with coarse, 
well defined lines of growth. Number of teeth eighteen, 
eight in front of the beaks. Teeth smallest near the beaks, 
wanting beneath the beaks. Denticles nearly parallel to 
a line drawn from the beaks through the greatest width of 
the shell. 
C. auburnensis differs from C. fecunda, the nearest al- 
lied species, in being smaller, proportionally much longer 
in front of the beaks, narrower in proportion to the 
length, and the denticles pointing away from the beaks at 
a smaller angle. 
This species is based on a large number of specimens. 
- Number 11517 of the invertebrate paleontological collec- 
tion of Walker Museum. 
CTENODONTA COSTATA, 0. Sp. 
Pl. vu. f. 7-8. 
Shell small, subtriangular, length and height subequal, 
thickness about one-third the height, compressed near 
