. 
SWALLOW AND HAWN—THE ROCKS OF KANSAS. 185 
rounded ridge extending from the beak to the middle of the 
ventral margin, and —— — the > posterior | side ; oar 
mangular =o the sides 
save a few irre lat epetugatious 
—o from beak to vanteat: margin, 0.95; length, 0. 70; 
of left valve, 0.16. 
jor Hawn’s collection from the — of the Cotton-wood, 
in Permian strata. 
Pectex ACUTIALATUS, Swallow. 
Shell small, depressed, polished, inflated part of the left 
_ Valve orbiculo-cuneate, rounded on the ventral margin; ante- 
rior wing i narrow, acuminate, separated from the side 
by a deep, rounded sinus, and a sharply-defined boundary 
from the s me cies abe: the back; posterior wing separated by a 
. us; cardi nal border a8 long, or longer, than. 
| the length of of the shell; no surface markings seen, save some 
faint indications of wide, depressed, radiating coste on the 
Hate at er the left valver Our specimens have n0- well- 
ht from base to ventral margin, 0.76. 
es trom the Preis —— = ea 
