S. Calvin—Shale at Independence, Iowa. 461 
x ese, two are not 
determined and five others are new to science, but the chief 
interest attaches to certain species that have hitherto been 
known only from the shales of bed No. 3, near Rockford, 
Iowa. For the purpose of indicating the relationship of the 
new shale to the other Devonian deposits of lowa, we shall 
arrange the specimens in three groups, using my manuscript 
: ’ 
era subumbona Hall. 
II. Species ranging through all the Devonian deposits, and 
so common to beds 1, 2 and 3: Aérypa reticularis Lin. 
_ IIL. Species common to beds 1 and 3, but not known to oecur 
in the intervening limestones: Strophodonta vata, D. Sp., 
S arcuata Hall, 8. Canace Hall and Whitfield, S. reversa Hall, 
Am. Jour. Sct.—THIrD Serres, Vou. XV, No. 90.—JuNz, 1878. 
31 
