PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 773 
short distance anterior to the cardinalia, extended anteriorly as a low ridge or 
dying out; lateral septa narrowly divergent anteriorly, an elevated and an- 
teriorly fimbriate adductor platform appearing on the outside of the septa. 
Genotype.—Craspedelia marginata Cooper, new species. 
Discussion —This genus is closely related to Bimuria as shown by the interior 
structure of both valves. Pedicle valves show a suggestion of a siphonate fora- 
men, but the specimens are more adult in their characters than B. immatura and 
B. siphonata with which it occurs. The deflected margins are clearly an adult 
character, and the genus may be regarded as an arrested off-shoot of the main 
Bimuria stock. 
The interior of the brachial valve in its adductor callosities also suggests an 
adult shell. These callosities are elevated in some instances to the same degree 
as the visceral disk of Leptellina and Bilobia. In this respect Craspedelia differs 
strongly from Bimuria. It is interesting to note that the adaptation of this shell 
as exhibited by the deflected margins is very much like Xenambonites. 
CRASPEDELIA MARGINATA Cooper, new species 
Plate 213, A, figures 1-20 
Shell small, transverse with the hinge forming the widest part; cardinal ex- 
tremities alate; lateral margins strongly oblique, gently convex; anterior margin 
broadly rounded. Surface smooth. 
Pedicle valve strongly convex in lateral profile and with the maximum con- 
vexity at the umbo; anterior profile strongly humped in the middle with steep 
slopes to the depressed flanks. Median region narrowly swollen and much ele- 
vated above the narrow, gently convex flanks. Marginal deflection not strongly 
elevated. Region immediately posterior to deflected rim forming a narrow trough. 
Brachial valve deeply concave in the median region; lateral extremities sul- 
cate but shallow; anterior part bounding concave median area steeply deflected 
toward the margin of the brachial valve; anterior margin deflected toward the 
pedicle valve, the deflected area attaining a length of more than 1 mm. Deflected 
margin enclosing the similar area in the pedicle valve. 
Measurements in mm.— Eeiten 
Brachial Hinge deflected 
Length length Midwidth width Height rim 
Paratype (117474a).... 4.4 ? 6.6 7.4 2.0 0.75 
iy (1874740). 0!. Set ? 5.0 6.2 1.9 0.90 
+ CLpzarawy eG. oc) P 3.1 6.0 7.0? ? 1.70 
Types.—Holotype: 117474b; figured paratypes: 117474a,c-f; unfigured para- 
types: 117474g-0. 
Horizon and locality——Pratt Ferry formation in Alabama: 0.2 mile southeast 
of Pratt Ferry, Blocton (15’) Quadrangle. 
Discussion—This species is like Bimuria matutina or B. immatura in the 
exterior form of the pedicle valve but differs in having the strong anterior rims. 
It differs internally from B. immatura in the different development of the callosi- 
ties of the adductor field. 
