SWALLOW—DESCRIPTION OF FOSSILS. 643 
SprrirER MIssouRIENSIS, N. sp. 
from fourteen to twenty; the shell is also ornamented by nu- 
merous fine concentric strie, and sometimes by conspicuous 
lines of growth. 
Verneuil (Geo, Rus Pl. VI, Fig. 9); but the Blassit is more 
gibbous and orbicular, the ison is higher, the plications less 
enerone and the beak of the dorsal wie much longer. 
ength, .63; width, .94; thickness, .44 
Abundant in the Chouteau Limestone of Cooper peansy: 
SprrirFerR CooPERENSIS, N. SP- 
Shell small, convex, transversely elliptical and (nial 
Concentric, punctate and plicate folds. Ve ral fy “eid Pid 
Convex, highest near the beak; mesial sinus sma i by 
tinct towards the beak, wide and shallow at the aia 
margin; lateral margins sharply rounded to the extre 
i, 
: . . en 
of the hinge line; area small, triangular, arched ; foram 
