PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 615 
Measurements in mm.— 
Brachial Greatest 
Length length Midwidth width Thickness 
Paratype (pedicle valve 117156e).. 13.7 ? 10.0 14.8 5.8 
7 (brachial valve 111329).. e 14.3 11.5 14.7 5.5? 
Types.—Holotype: 117156-1; figured paratypes: 111329, 117155b,c,e-g, 
117156a,c-h,j; unfigured paratypes: 117155a,d, 117156b,i,k,m. 
Horizon and locality—Lower 3 feet of the Pratt Ferry formation in Alabama: 
0.2 mile southeast of Pratt Ferry, Blocton (15’) Quadrangle. 
Discussion.—No other shell is quite like this one except for species of Idio- 
strophia. The latter have the elongate form and pentagonal outline of Parallelel- 
asma and the peculiar flattening of the margins, but the interiors of the two 
genera are so different that little confusion will result. 
Genus SALONIA Cooper and Whitcomb, 1933 
SALONIA MAGNAPLICATA Cooper and Whitcomb 
Plate 107, D, figures 15-21 
Salonia magnaplicata Cooper and Wutrcoms, Journ. Washington Acad. Sci., vol. 23, No. 11, 
PP. 500-503, 1933. 
Figures of this species are introduced for comparison with those of Parallel- 
elasma. The presence of the long subparallel brachiophore supporting plates in- 
dicates relationship between the two genera. They differ mostly in exterior orna- 
mentation and form but also in one important interior feature. The brachial 
processes of Salonia are long, flat, somewhat curved blades, whereas those of 
Parallelelasma are short, straight, and blunt. 
Types.—Holotype: 85422a; paratypes: 85422b-e,p. 
Horizon and locality Salona formation (12 feet above the base) in Pennsyl- 
vania: Along the railroad beside Fishing Creek in Salona, Clinton County, Lock 
Haven (15’) Quadrangle. 
DIDYMELASMA Cooper, new genus 
(Greek didymos, twin; elasma, plate) 
Shell small, syntrophoid in appearance; uniplicate ; surface paucicostate. Beaks 
small, interareas obsolete. Delthyrium open. 
Pedicle interior provided with a narrow, short spondylium supported by a 
long, thin median septum. 
Brachial interior with two long parallel plates supporting a long, thin, slightly 
curved brachial process, which is attached to a triangular socket plate located 
between the posterior edge of the brachial process and the posterior edge of the 
valve. Muscle scars not seen. 
Genotype-——Didymelasma longicrurum Cooper, new species. 
This genus is so far known only from the species described herein. It is a 
small shell having the appearance of a syntrophid. It has small beaks with no 
interarea remaining as far as can be determined, The species is not unlike that 
