PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 189 
Order ATREMATA Beecher, 1891 
Superfamily OzsoLacea Schuchert, 1896 
Family OBOLIDAE King, 1846 
Obolacea with thickened and striated pedicle regions traversed by a pedicle 
groove. Life habits as in modern Lingula. 
Recovery of superb corneous brachiopod material by the use of acetic acid 
has permitted a better understanding of some of the genera assigned to this 
family. It is now clear that “Obolus” and “Lingula”’ are composite groups con- 
sisting of many genera. Specimens recovered from the Pratt Ferry limestone 
of Alabama permit wider identification of Lingulella. The type of that genus is an 
Ordovician fossil, but the genus itself has been widely identified, probably cor- 
rectly, in the Cambrian. A number of species herein described have the apical 
characters of Lingulella and are so assigned. A number of others are tentatively 
referred to this genus rather than Lingula because no Ordovician specimens 
with the beak characters of Lingula were seen in the material herein described. 
Subfamily OxsoLtinaAre Dall, 1870 
Usually round or broadly oval forms with pedicle groove. 
Genus OBOLUS Eichwald, 1829 
OBOLUS ? BICONVEXA Cooper, new species 
Plate 8, A, figures I-3 
Shell small, broadly oval in outline with strongly curved margins; subequally 
biconvex ; surface marked by concentric undulations. Pedicle valve moderately 
convex but with the greatest convexity just anterior to the middle; anterior slope 
short and steep. Anterior profile of pedicle valve broadly convex and with short, 
steep lateral slopes and with median region swollen. 
Brachial valve fairly strongly convex with the greatest convexity located in 
the umbonal region and its vicinity ; anterior slope long and gentle ; anterior pro- 
file moderately convex, somewhat narrowed medianly. Interiors unknown. 
Measurements in mm.— 
Length Width 
Ftolarype (pedicle “valye):’ .s.. 2.0.0. inn vena ene os eee 5.9 5.4 
Paritype, (orachtal valve TIG78ep) . 0). c date een. se 4.8 4.6 
Types.—Holotype: 116788c; figured paratypes: 116788a,b. 
Horizon and locality—lLower Paperville formation in Tennessee: On the 
slope just south of the Southern RR. cut, 1 mile west of Mosheim, Mosheim 
(T.V.A. 181-NW) Quadrangle. 
Discussion—This species suggests O. nitens Cooper, new species, from a 
similar position in the Rich Valley in a more western belt, but differs in the 
lesser regularity of its ornamentation, the stronger biconvexity, and smaller size. 
