PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 611 
former specimen. Neither specimen gives clear indications of its true generic 
affinities. 
Figured specimens.—111371a,b; 117178. 
Horizon and locality—Pogonip group (Orthidiella zone) in Nevada: In the 
first ridge east of Frenchman Flat, Las Vegas (1°) Quadrangle; about 1 mile 
above the mouth of Whiterock Canyon, Monitor Range, Roberts Mountains (1°) 
Quadrangle. 
PORAMBONITES ? sp. 4 
Plate 107, C, figures 12-14 
A crushed specimen of this genus, probably a brachial valve, is 13 mm. long 
and 15.8 mm. wide. The valve is swollen and tumid, particularly in the umbonal 
region. It is very delicately ornamented, having 4 to 6 costellae in I mm. at the 
front. The umbonal region is very finely ornamented. Pits fine, about 5 to the 
millimeter at the front. 
Figured specimen.—Columbia Univ. 26404 (1093). 
Horizon and locality.—Salona formation in Pennsylvania: From the roadside 
and small quarry on Pennsylvania Highway 44, 150 yards east of the road to 
Oriole, east of Antes Gap, Williamsport, (15’) Quadrangle. 
Discussion.—This genus is very rare in any of the known Ordovician rocks 
of the eastern United States. The specimen here figured is not well enough pre- 
served to describe. Dr. G. Marshall Kay who found it identified the beds from 
which it was taken as Upper Rodman, but it occurs in shaly beds that seem best 
referred to the lower part of the Salona formation. 
Suborder PENTAMEROIDEA Schuchert and Cooper, 1931 
Superfamily PENTAMERACEA Schuchert, 1896 
Family PARALLELELASMATIDAE Cooper, new family 
Shells having a spondylium duplex in the pedicle valve. Brachial valve pro- ' 
vided with long subparallel plates defining a deep notothyrial cavity. 
PARALLELELASMA Cooper, new genus 
(Greek parallelos, parallel; elasma, plate) 
Shell 4 inch in length or longer, irregularly pentagonal in outline with narrow 
beaks and a wide anterior. Rectimarginate to broadly and indistinctly uniplicate. 
Biconvex ; valves subequally deep; interareas reduced or obsolete; delthyrium 
open ; ornamentation paucicostate, the posterior smooth and the anterior costate. 
Pedicle interior with long, curved, slender teeth; notothyrial cavity V-shaped, 
defined by thin, delicate dental plates that unite with the median septum to form 
a spondylium; anterior of spondylium produced into an elongate, narrowly 
rounded, concave tongue. Median septum, high, slender, prolonged anterior tc 
the spondylium, not extending to the middle. 
Brachial valve with deep and narrow notothyrial cavity; brachiophores short, 
