THE KIMMSWICK AND PLATTIN LIMESTONES 
223 
appendix: SILURIAN SPECIES 
44. Platymerella manniensis Foerste 
Plate XXIII, figs, 5 A-H 
Platymerella manniensis Foerste, originally described from the 
Brassfield of western Tennessee, and later found by Savage in 
the basal part of the Sexton Creek equivalent of the Brassfield in 
northeastern Missouri and adjacent Illinois, and also in the 
northeastern corner of Illinois, has been found recently in 
the basal layers of the Brassfield at Lawshe, in Adams County, 
Ohio. The Lawshe specimens are of special interest on account 
of exposing the interior of the valves. Viewed from the exterior, 
the dissociated valves are so closely similar that it is difficult to 
distinguish the pedicel valves from the brachial ones. When 
attached to each other, the umbo of the pedicel valve rises farther 
above the hinge-line, so that the beak is more curved. 
Pedicel valve (figs. 5 A, B, C, D) with an oval or rhomboid 
spondylium, about 5 mm. long, strongly divergent from the 
surface of the interior of the valve, and supported by a thin, 
tall median septum which disappears within 5 mm. from the 
anterior margin of the spondylium. Pitted ovarian markings 
are present on the posterior part of the interior. 
Brachial valve (figs. 5 E, F, G) with two short crural plates, 
about 3 or 4 mm. in length, converging along the median line 
and forming a cruralium resting directly upon the bottom of 
the interior of the valve. The crural prolongations of the an- 
terior margin of the crural plates rarely are preserved. Along 
the median line of the shell the anterior part of the cruralium 
is prolonged into a low and narrow septal line. In one speci- 
men (fig. 5 H) the crural plates rest directly upon the bottom 
of the interior of the valve, and are prolonged anteriorly into 
two sharp parallel ridges, about a millimeter in height, 3 or 4 
mm. long, and slightly over 2 mm. apart. 
The genus Platymerella is characterized by its flattened, 
elongate form; the absence of a cardinal area; the delthyrium 
is concealed entirely by the contact of the beaks of the two 
