374 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
marble) in Virginia: On the road beside Yellow Branch, 5 miles southeast of 
Rose Hill, Rose Hill (T.V.A. 161-NW) Quadrangle. 
Discussion.—This species is characterized by its rectangular form, the an- 
teriorly nearly obsolete brachial sulcus, and the fine costellae. Some pedicle valves 
show the development of a distinct sulcus at the front margin, and the cor- 
responding part of the brachial valve is so swollen that the sulcus is obliterated. 
This species is quite unlike any of those described herein. It differs from G. con- 
cinnula by its anteriorly obsolete brachial sulcus and much more subdued cos- 
tellae. It is a much smaller shell than G. assimilis with finer costellae and less 
pronounced sulcus. 
GLYPTORTHIS SUBCARINATA Cooper, new species 
Piate 46, D, figures 18-23 
Shell small, wider than long with the hinge about equal to or slightly less than 
the width at the middle. Sides rounded; anterior margin truncated. Anterior 
commissure sulcate. Surface multicostellate, costellae numbering about 30, sepa- 
rated by striae about equal to the costellae in width. 
Pedicle valve moderately convex in lateral profile with the deepest part near 
the middle; anterior profile narrowly convex with moderately steep lateral 
slopes; umbo narrowly convex, the convexity and a strong median costella ex- 
tending to the front margin as a subcarinate fold; median and anteromedian 
region somewhat swollen with long, fairly steep lateral and posterolateral slopes. 
Interarea nearly catacline. 
Brachial valve fairly evenly and gently convex in lateral profile; moderately 
convex and medianly deeply sulcate in anterior profile; umbo somewhat swollen, 
deeply sulcate; sulcus deepening and widening anteriorly to the front margin. 
Flanks bounding sulcus swollen; lateral and posterolateral slopes short and 
gentle. 
Measurements in mm.—Holotype, length 6.6, brachial length 6.3, width 9.1, 
hinge width 8.2, thickness 3.7. 
Type.—Holotype: 117987. 
Horizon and locality—Lower Sevier formation in Tennessee: 4+ mile north- 
east of Miser, Louisville (T.V.A. 138-SE) Quadrangle. 
Discussion.—This is a small species having the appearance of G. uncinata but 
not so deeply sulcate nor so strongly costellate. It is much more strongly sul- 
cate than G. uniformis and is also, at least as now understood, a somewhat 
smaller shell. 
GLYPTORTHIS SUBCIRCULARIS Cooper, new species 
Plate 49, G, figures 33-40 
Shell large for the genus, slightly wider than long and with the hinge con- 
siderably narrower than the greatest width which is at the middle, sides rounded, 
anterior margin gently rounded to truncated. Anterior commissure gently 
uniplicate ; valves subequally convex; surface multicostellate, costellae broadly 
angular, 5 in 5 mm. at the front margin. 
