SWALLOW AND HAWN—THE ROCKS OF KANSAS. 195 
the obtuse acs of the dorsal ma rgin; : suture di- 
vided b Bs longitudinal elevated ‘ridge, in ap ita valves 
—" wards the ventral margin where they meet at an 
I ht, 0 ongate, arch 
anterior sho rt, rounded; dorsal short, depressed, and strongly 
eurved up at the posterior imei L ; ‘external ligament nearly 
as long as the cardinal er. 
Dimensions of a large spe :-—Length, 2.31; greatest 
bréadth at the posterior extremity of the cardinal border 
1.26; greatest thickness near the middle, 1.115 thickness at 
posterior extremity, 1.02. 
Missouri State collection, from the Middle Coal Reais 
near Lexington; and Major Hawn’s collection from the Per- 
mian rocks, 1 in the valley of the Cotton-wood, K. T. 
heii banpepnordits ORBICULARE (?), Goldfuss, a 135, 
fig. 10, p- 196. 
= Dee specimen isa a cast, ant it agrees in size and form with 
“the east figured and described by Goldfuss from the Muschel- 
_ kalk of German: 
ih y: 
From No. et. the Triassic @) System, K. T T. | 
2 Ae bites 
oe Hawai in the > valley of the ——. 
