PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 237 
sides of the central scar and also a short distance posterolaterally of the central 
scar. Two pits appear on each side of the median line and just anterior to the 
pedicle notch, and anterolateral to these and close to the margin occur another 
pair of muscles. 
The brachial valve is characterized by a strong and deep umbonal muscle pit. 
From this pit 2 pallial trunks extend anterolaterally for about one-third the 
length of the valve. Two small muscle scars are located near the center, but other 
scars are obscure. 
Genotype—FPaterula bohemica Barrande, Syst. Sil. Centre Bohéme, vol. 5, 
p. 110, pls. 95, 152, 1879. 
Discussion.—Little has been known of this peculiar genus because its shells 
are generally very rare. Until the present writing a single species, P. amit, was 
known in North America. Excellently preserved specimens occur in many parts 
of the Southern Appalachians from Alabama to Pennsylvania which afford new 
information on the genus. Unfortunately, the specimens are so small and the 
muscle marks so faintly impressed that description of the interior is difficult. 
One of the most striking features of the pedicle interior is the occurrence of 
a fine impressed line originating just anterior to the pedicle notch. This line 
divides, and the 2 branches extend anteriorly to about the middle of the valve. 
Anterior to the end of these lines occurs a network of minute pallial impressions 
that radiate anteriorly, anterolaterally, and laterally. 
The muscle system of the pedicle valve is difficult to establish, but it seems 
certain that the following are present: 2 small umbonal muscles, a large central 
one, 2 pairs of small muscles occurring anterolateral and posterolateral to the 
central one, and a pair or 2 pairs anterolateral to the pedicle notch and located 
just under the margin. 
The interior of the brachial valve is less clearly defined in the specimens avail- 
able. The big umbonal muscle patch with the 2 short but prominent pallial trunks 
diverging from it are the most striking features. 
In the rocks under consideration Paterula occurs rarely in the Arline forma- 
tion but it is common in the Botetourt and Oranda formations. It occurs in the 
Liberty Hall facies, and two specimens are known from the Trenton of New 
York. The genus has been taken in the Bromide and Viola formations of Okla- 
homa. It is thus evident that it may be expected in any rocks from Black River 
to high Trenton. The genus is most abundant in bituminous limestones or lime- 
stones associated with black shales such as those of the Botetourt, Oranda, and 
Liberty Hall facies between Harrisonburg and Winchester, Va. Specimens are 
very abundant in the Pratt Ferry formation at Pratt Ferry, Blocton Quadrangle. 
These limestones yield large numbers of specimens when the blocks are dissolved 
in acetic acid. The Botetourt limestone in the vicinity of Strasburg, Va., yields 
free specimens on etching with hydrochloric acid. The same treatment will yield 
small numbers of specimens from various parts of the Nidulites zone of the 
Edinburg formation. 
The genus also occurs in abundance in limestones of the Table Head forma- 
