592 TRANS. OF THE ACAD. OF SCIENCE. 
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others bifid or trifid; inferior lateral lobe very small, scarcely 
The diameter of the largest specimen (imperfect) in the 
collection is six inches. A young specimen gives for diame- 
ter, 34 inches; width of last volution 144 inches; thickness, 
1,45 inches. : 
Form, and Locality.—This is the most beautiful species of 
“Immonite we have found in the Cretaceous strata of Texas, 
and quite characteristic of the marls and calcareous sand- 
stones forming the base of the formation. f 
curs in Grayson County, four and a half miles north 0 
Sherman, and Bluffs of Red River, in Fannin and Lamar 
Counties. 
A. MEEKIANUS, 0. sp. 
Shell large, discoidal, compressed (number of volutions un- 
known); transverse section of last volution subquadrate 
subcircular; sides flattened convex; dorsum, broad, flat, oF 
ws 
b 
Where they are slightly swelled or subnodose, 
at the dorsal margin, each in a remarkably prom 
suptriangular at base and with the extremity directe 
y- 
minent node, 
d late- 
