PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 853 
Pedicle valve gently convex in lateral profile; anterior profile gently convex 
but with the median region narrowly and sharply pinched in the middle; umbo 
and median region somewhat narrowly swollen to form an indistinct fold that dis- 
appears at the place of geniculation. Visceral region 8 to 9 mm. long; posterior 
slope of trail short; trail short, moderately steep. 
Brachial valve fairly evenly and gently convex in anterior and lateral profiles ; 
median region marked by an indistinct sulcus; flanks gently convex; trail short. 
Measurements in mm.— 
Length 
Brachial Hinge Thick- aoc Trail 
Length length Midwidth width ness region length 
FiGlotype fd OS. 11.4 ? 16.4 18.0 1.5 9.0 2.0 
Paratype (117661a).... 13.0 ? 16.8 20.5 215 8.5 5.0 
ss (027662) / 3... 40? 8.3 10.8 11.6 1.4 8.3 ? 
c (i17662e)))-2 .. ? 10.7 13.6 18.0 2 8.3 250° 
Types.—Holotype: 117662a; figured paratypes: 117661a,b, 117662b-d; un- 
figured paratypes: 117662e-i. 
Horizon and locality.—Edinburg formation (Cyrtonotella zone) in Strasburg 
(15’) Quadrangle, Virginia: On the railroad at the switch and in the ravine 
about 4 mile east of Strasburg Junction; on the south side of the road 0.2 mile 
east of Strasburg Junction. 
Botetourt formation: Same as above. 
Discussion.—This species is represented by about 25 specimens, but not one of 
them is a complete valve except the holotype. Several of the specimens evidently 
represent immature forms that have not yet developed the trail. One very poorly 
preserved specimen from the ravine east of Strasburg Junction shows this species 
to have been nearly as large and extravagantly developed as L. insueta from 
the Rodman formation of Pennsylvania. The specimen referred to preserves 
part of the trail which is 8 mm. long. 
This species differs from L. imsueta in having stronger and more regular 
wrinkles along the posterior margin and in having a shorter trail. 
LIMBIMURINA INSUETA Cooper, new species 
Plate 220, D, figures 18-23; plate 221, F, figures 37-42 
Shell variable, attaining an inch in length and width; subquadrate to subrec- 
tangular in outline; sides nearly straight; anterior margin broadly rounded ; 
surface finely costellate ; visceral region marked by fine irregular wrinkles. 
Visceral region of pedicle valve gently convex in both profiles ; umbo narrowly 
swollen; median region gently swollen to form an indistinct fold; flanks flat- 
tened. Place of geniculation about 9 mm. anterior to the beak. Posterior slope 
of trail long and steep; trail variable, usually fairly long. 
Brachial valve gently convex in lateral and anterior profile; visceral region 
bounded anteriorly by a sharp rim; umbo sulcate; sulcus somewhat obscure an- 
terior to the umbo; flanks gently convex; posterior of trail marked by a deep 
trough peripheral to the visceral area; trail long. 
