PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 765 
BIMURIA BUTTSI Cooper, new species 
Plate 212, B, figures 11-31 
Christiania lamellosa Ulrich Ms. (not Bassler, 1919), Butrs, Alabama Geol. Surv., Special 
Rep. 14, p. 116, pl. 26, figs. 31-34, 1926. 
Shell of about medium size for the genus, slightly wider than long; hinge less 
than the greatest width which is at the middle of old adults. Lateral margins 
gently convex; anterior margin broadly to narrowly rounded. Umbonal region 
of both valves usually smooth, remainder of surface covered by concentric 
lamellae. 
Pedicle valve moderately convex in lateral and anterior profiles. Umbo swol- 
len. Anteriorly from the umbo a distinct but low fold is developed which ex- 
tends to the anterior margin and produces a shallow sulcus there. Lateral slopes 
moderately steep; posterolateral slopes abrupt and steep. Interarea strongly 
curved, anacline. 
Brachial valve strongly concave with the greatest depth in the midregion; 
anterior portion sulcate; flanks bounding sulcus gently concave. Umbonal re- 
gion deeply concave; interarea strongly hypercline. 
Pedicle interior with small teeth, vascula media well impressed in adults; 
other pallial marks less distinct. Inside the brachial valve lateral and median 
septa well developed ; adductors located on callosities, and fairly well impressed. 
Measurements in mm.— 
Brachial Hinge Thick- 
Length length Width width ness Height 
FIOIOUYDE. Jaco s a cainy Sogs ee's ves 5g 15.6 12.0 18.5 15.2 4.0 6.8 
Paratype (110032a with frills).. 18.4 15.0 21.9 16.2 47 9.2 
f (a1eosah GAR. 14.4 II.0 15.6 123 4.0 6.9 
- Gi Cee) ee ee 10.9 8.9 11.9 13.0 2.2 5.0 
re CFESOOD) erccaiats Saieai sie > os 17.3 14.0 18.8 16.3 3.7 7.6 
Types.—Holotype: 1109344, figured paratypes: 71506a, 110930a-d, 110932a,e, 
110933a,c-e, 110934b,c, 110935a, 123264; unfigured paratypes: 71506b, 110930e, 
110931, 110932b-d, 110933b, 110935b-e. 
Horizon and locality.—Little Oak formation in Alabama: 4 mile northeast of 
Pelham and 2 miles north of Pelham, Bessemer Iron District (15’) Quadrangle; 
intersection of Bailey Gap road with main road 13 miles northeast of Newhope 
Church, SW4iSW3 sec. 13, T. 19 S., R. 2 W., Vandiver (15’) Quadrangle. 
Discussion.—The young of this species are generally considerably wider than 
long and with the hinge forming the greatest width. With increasing age the 
length increases at the expense of the width with the result that the old adult is 
generally subquadrate to subcircular in outline. The hinge with increasing age 
fails to grow lateraily. Consequently, in adult shells the hinge does not form 
the widest portion of the valves. 
This species suggests B. superba which it approaches in size, but it seldom 
attains the large subquadrate form of the Tennessee species. The development 
of a fold and sulcus are features lacking in B. superba. The fold and sulcus are 
seldom very prominent in B. buttst, but they are, nevertheless, distinct. The 
