NOTES ON THE GENUS ATRYPA 19 
and Iowa Devonian—will be awaited with special interest. The 
prevailing form of Atrypa aspera var. occidentalis as it occurs in the 
Iowa Devonian, is illustrated by Hall in Plate 6, Fig’s. 34,—3b, 
Vol. 1; Part I, Iowa Geological Survey, 1858; and in Plate 53A, 
Fig’s, 19-21 Paleontology of N. Y. Vol. 4. 
Atrypa lineata var. inflata N. Var. 
This form differs widely from A. lieata, but it has seemed best 
to consider it as a variety of this species. It is a well marked variety, 
being very uniform in outline and form; is longer than wide, more 
or less sharply rounded in front; very evenly and strongly inflated 
especially the dorsal valve, while the ventral valve sometimes has a 
broad even concave area in front; beaks small and sharply incurved; 
perforation small; hinge line less than greatest width of the valves, 
straight or broadly triangular. Surface marked by fine striae, 
sometimes implanted and bifurcating. 
Position and locality: From lower Stromatopora reef, upper 
part of the Middle Devonian, at Scriptures quarry and Bloody 
Run, three miles southeast from Charles City, Iowa, and from a 
few other localities in Iowa. 
Now in the author’s collection. 
Atrypa devoniana N. Sp. rae 
Plate VIII. Figs. 9-11. 
Shell ranging from small to medium size, orbicular to sub- 
orbicular in marginal outline, and sometimes longer than wide. 
Ventral valve flattened or gently concave and much more promi- * 
nently so in the umbonal region; front part of the valve generally 
somewhat concave or developing a slight to profound undefined 
sinus; beak low, sharply incurved, area closed and perforation 
usually very distinct. Dorsal valve generally very convex especi- 
ally so just above the centre, and in young and immature forms 
less prominently so. Surface marked by many fine striae which 
are increased by bifurcation and implantation, but almost wholly 
so by the former; and generally crossed by faint or sometimes 
slightly prominent lines of growth, but sometimes this feature is 
wanting. This is the most beautiful species of the genus occurring 
in the Hackberry Group, and is constant in form and expression 
throughout its life history. 
Position and locality: Occurs abundantly throughout the 
