PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 385 
Discussion—tThis species is larger than the other two known species, 
E. nicklesi Foerste and E. rogersensis Foerste, and the fold and sulcus originate 
nearer the beak than in either of the other two. 
Genus PTYCHOPLEURELLA Schuchert and Cooper, 1931 
Ptychopleurella ScHUCHERT and Cooper, Amer. Journ. Sci., ser. 5, vol. 22, p. 244, 1031; 
Mem. Peabody Mus. Nat. Hist., vol. 4, pt. 1, p. 92, 1932. 
This genus is composed of a considerable number of species, all of small size. 
The pedicle valve is characterized by a hemipyramidal profile and a long palin- 
trope bisected by a narrow delthyrium. The delthyrium is often restricted by 
lateral plates along its sides. In addition to the lateral plates the apex of the 
delthyrium may be occupied by a small plate slightly depressed below the delthy- 
rial edge and usually more or less concave. This plate may be the seat of pedicle 
attachment and occupies the position of the pedicle scar and the pseudodeltidium 
of other genera. Internally the muscle field is like that of Glyptorthis, but the 
dental plates, which are of the receding type, are much reduced. 
The brachial valve is generally more or less strongly convex and has all the 
internal details of Glyptorthis. Generally the median ridge is more elevated and 
slender than usual in Glyptorthis, and the cardinalia are ponderous for such a 
small shell. 
The most distinctive features of this genus are on the exterior. The pedicle 
valve is always provided with a prominent median costa which may be elevated 
or depressed and which usually is accompanied by 2 or 4 additional costae that 
form a more or less distinct fold. Not infrequently the median costa may be de- 
pressed below the level of the fold. The brachial valve is characterized by a 
corresponding deep sulcus. 
Ptychopleurella is not common in the rocks studied. The most prolific locality 
for the genus and one yielding exquisite specimens, with proper handling, is the 
Porterfield Quarry, 5 miles east of Saltville, Va. Here it occurs in the thin lime- 
stone layers of the transition beds from the Effna formation to the Rich Valley 
formation. Fossils in the broken pieces of limestone lying on the dumps about 
the quarry are silicified, and the specimens can be etched free of the matrix, 
Species not described because of insufficient material occur in the Benbolt forma- 
tion at Rye Cove, Va., and at two levels in the Edinburg limestone, 4 mile 
east of Strasburg Junction, Va. 
PTYCHOPLEURELLA GLOBULARIS Cooper, new species 
Plate 43, D, figures 9-17; plate 82, H, figures 33-39 
Shell small for the genus, subrectangular in outline but with rounded angles; 
unequally biconvex, the pedicle valve having about two-thirds the depth of the 
brachial valve; hinge slightly narrower than the greatest shell width; sides 
slightly rounded or nearly straight ; anterolateral extremities rounded; anterior 
margin truncated ; anterior commissure rectimarginate to slightly sulcate; sur- 
face multicostellate, costellae subangular, distant, separated by spaces about twice 
