94 
Aug. F. Foerste 
Rhynchotreta simplex, sp. nov. 
{Plate III, Figs. 46, A, B.) 
Shell triangular, cuneiform, tapering posteriorly into an angular 
beak. Width of one specimen, ii mm.; thickness, 5 mm.; length, 
estimated at 13 mm. Both valves moderately convex. In the 
pedicel valve the teeth are supported by thin vertical lamellae 
which border a long, narrow, deep pedicel scar; muscular impres- 
sions faint, probably 3 mm. long, extending to within 8 mm. of the 
anterior margin of the shell. Brachial valve with a median septum 
Cardinal slopes long and flattened. Plications about 12; no evi- 
dence of fold or sinus. Shell apparently remaining in the neanic 
stage. No reversal of curvature is noted. 
Compared with Rhynchotreta transversa, Weller, this species 
has a greater number of plications. 
Clinton bed: from the weathered brown chert found near the 
cement mill, at the southern end of Clifton, along the river. Ten- 
nessee. 
Rhynchotreta thebesensis, sp. nov. 
{Plate IV, Figs. 66, A, B, C.) 
Shell cuneiform, with long flat sides diverging at an angle of 6o° 
to 70°, with an acuminate beak. The anterior outline is rounded, 
and the depth of the shell is considerable for one of this type. In 
a shell having a width of 14.5 mm., the depth was 10.5 mm., the 
length of the brachial valve was 14.5 mm., and the length of the 
pedicel valve was estimated at slightly over 15.5 mm. Near the 
beak of the brachial valve a few specimens show a slight median 
concavity. The two median plications are slightly raised ante- 
riorly above the general convexity of this part of the shell. On 
each side of these median plications there are four distinct and i 
indistinct plication, reduced sometimes to 3 distinct and i indis- 
tinct one. On the pedicel valve there is a median plication with 
4 distinct and i indistinct plication on each side. This median 
plication, in some specimens, terminates in a slight depression 
anteriorly, in others the plication on each side of the median pli- 
cation also is involved so that there is a broad flattening or slight 
depression, without the appearance of a sinus. There is no evi- 
dence of a deltidium partly closing the delthyrium. 
Strata of uncertain age, but evidently lower Niagaran. Thebes, 
Illinois. 
