PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 851 
MURINELLA sp. 2 
Plate 217, A, figure 1 
Large, transversely semielliptical in outline, with the hinge equal to or slightly 
less than the greatest shell width ; sides rounded, slightly oblique. Anterior mar- 
gin broadly rounded; surface marked by alternating strong and fine costellae. 
Pedicle valve unevenly convex in lateral profile, the most convex part being 
the middle ; anterior profile broadly domed. Posterior half or more gently convex 
to nearly flat ; anterior half somewhat abruptly bent toward the brachial valve to 
form a long trail which is gently convex in lateral profile. Muscle area small, 
subcircular. Brachial valve nearly flat. 
Figured specimen.—117648a. 
Horizon and locality —Tulip Creek formation in Oklahoma: On west branch 
of Sycamore Creek, sec. 27, T. 3 S., R. 4 E., Johnston County. 
MURINELLA sp. 3 
Plate 226, A, figures I, 2 
A single brachial valve is nearly flat in lateral and anterior profile and is 
marked by distant, strong costellae separated by numerous (as many as IT) 
fine costellae all cancellated by fine concentric lines. The interior is distinctly 
leptaenoid with a broad notothyrial platform surmounted by a small, delicate 
leptaenoid cardinal process. The muscle area is indistinct and a double sub- 
peripheral rim suggests the type of structure in the brachial valve of Murinella. 
Figured specimen.—117649. 
Horizon and locality—Little Oak formation (top third) in Alabama: 1 mile 
north of Pelham, Bessemer Iron District (15’) Quadrangle. 
LIMBIMURINA Cooper, new genus 
(Latin limbus, border; murus, wall) 
Shell attaining a length and width of about 1 inch; subrectangular to semi- 
elliptical in outline; compressed biconvex in profile; anterior and sides marked 
by an elaborate frill geniculated toward the pedicle valve. Visceral region marked 
by irregular wrinkles; entire surface marked by fine costellae and concentric 
lines of growth. 
Pedicle valve with small foramen, strong divergent dental plates, a moderately 
large, subcircular muscle area surrounded by elevated ridges extending from the 
dental plates and a short low, median ridge dividing the muscle field and extended 
some distance anterior to it. 
Brachial interior with thin, bladelike brachiophores, wide sockets, moderately 
thick notothyrial platform bearing a cardinal process consisting of 2 short 
shafted prongs with concave myophores. Adductor field with prominent oblique 
ridges. 
Genotype.—Limbimurina insueta Cooper, new species. 
Discussion.—The distinctive feature of this genus is the elaborate frill which 
