PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 335 
PRODUCTORTHIS AGILERA (Willard) 
Plate 56, B, figures 6-25 
Nicolella agilera Wittarp, Bull. Mus. Comp. Zool., Harvard Coll., vol. 68, No. 6, p. 272, 
pl. 3, fig. 7, 1928. 
Shell large for the genus, slightly wider than long, with the width of the hinge 
less than or greater than the width at the middle. Cardinal extremities in young 
specimens acute but in adults or old individuals forming a right angle or obtuse. 
Sides oblique to rounded and the anterior margin broadly rounded. Surface 
marked by distant costellae, 3 to 6 in the space of 5 mm. at the front margin. 
Lamellae numerous and closely crowded anteriorly. 
Pedicle valve moderately convex in lateral profile with the most convexity in 
the posterior half; anterior profile broadly convex, with long moderately steep 
slopes. Umbonal and median regions full with steep umbonal slopes and mod- 
erately steep lateral slopes. Anterior slope long, moderately steep. Beak in- 
curved, beak and umbo protruding posterior to the posterior margin. Interior 
with deep delthyrial cavity, thickened muscle platform with adductor track. 
Diductor scars long and slender. 
Brachial valve moderately convex with the front third somewhat flattened ; 
anterior profile broadly and gently convex with the margins more or less re- 
flected in a brachial direction. Median region swollen gently with gentle slopes 
leading into shallow troughs produced by the margins which are deflected in the 
direction of the brachial valve. Interior with ponderous cardinal process and 
short, low median ridge. Adductor field small, rectangular. 
Measurements in mm.— 
Hinge 
Length Width width Thickness 
PROLOG A iste ois 6 i0/a 5-6 oat ee bets 17.5 18.7 21.9? 3.90 
Hypotype (1o9890d) ............. 27.3 31.0+- 24.0+- 11.5 
ie (brachial valve 1o9891a). 15.6 22.6 23.2 ? 
Types—Holotype: M.C.Z. 8607; figured hypotypes: 1098goa-d, 1o9891a,f,g, 
1og8g5a-c, 109896; unfigured hypotypes: 10g890e-h, I0g989ib-e, r1o9895d, 
109899b-d ; figured specimen: 109899a. 
Horizon and locality —Effna formation in Virginia: Porterfield Quarry, 5 
miles east of Saltville, Maccrady (T.V.A. 218-NW) Quadrangle; McNutt 
Quarry 12 miles southwest of Bland, Burkes Garden (15’) Quadrangle. 
Discussion—tThis is the largest species of the genus known in either North 
America or Europe and differs from its nearest relative P. americana in its 
greater size, less swollen pedicle valve, less convex brachial valve, and stronger 
ornamentation. 
All the specimens from the Effna formation have been placed under this species 
although considerable discrepancy in their size occurs. None of the specimens 
taken from the hard limestone show the ornamentation in detail, but it seems 
to be about the same as that of the material taken from the shaly beds on the 
Porterfield reef. Most of the limestone specimens break out as a core leaving the 
