488 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
north of the road on Buffalo Creek, 24 miles west of Murat, Natural Bridge 
(15’) Quadrangle. 
Discussion.—This species is characterized by its fairly large size and strongly 
convex valves. In these respects it is similar to M. biconvexa and M. globosa. 
It differs from the former in having a rectimarginate anterior margin, and from 
the latter in having a much more strongly convex pedicle valve. This species is 
different from all the pre-Benbolt species in the subequal depth of its valves. It 
is more finely costellate than 1. tumida and is larger and more convex in both 
valves than M. laticardinia. 
MIMELLA VULGARIS (Raymond) 
Plate 85, A, figures 1-12; plate 92, E, figures 29-33 
Hebertella vulgaris RayMonp, Ann, Carnegie Mus., vol. 3, p. 501, 1906; ibid., vol. 7, No. 2, 
Pp. 242, text fig. 16, pl. 36, fig. 3, I91T. 
Shell of about medium size for the genus, somewhat variable; wider than 
long, somewhat rectangular in outline and generally with the hinge only slightly 
less than the width ; cardinal extremities usually slightly obtuse. Sides very gently 
rounded ; anterior margin broadly rounded; anterior commissure rectimarginate 
to faintly uniplicate. Surface costellate, costellae usually narrowly rounded, dis- 
tant and numbering 6 to 9 in 5 mm. at the front margin at or near the middle. 
Costellae direct from umbo where bifurcation and intercalation takes place. 
Pedicle valve unevenly convex in lateral profile, the posterior half gently con- 
vex and the anterior half flattened; anterior profile forming a broad triangle 
with long, gently sloping sides and broadly rounded apex. Umbonal region some- 
what swollen, the swelling continuing to about the middle; anteromedian region 
flattened ; lateral slopes short, steepening to the cardinal extremities. Beak gently 
curved ; interarea moderately long and strongly apsacline. 
Brachial valve moderately convex in lateral profile with maximum convexity 
in the umbonal region; anterior profile moderately domed and with steep lateral 
slopes; beak fairly strongly incurved; umbo and median region fairly strongly 
swollen; sulcus originating on the umbo at the beak, shallow and inconspicuous, 
widening slightly and nearly disappearing at the anterior margin. Flanks bound- 
ing sulcus moderately swollen and with short, steep lateral slopes. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Eiolatype Cl) Us veces bev et ees 10.3 0.7 11.8 9.6 ? 
Hypotype (110790a)......... 12.6 12.0 14.8 II.9 8.0 
sf GTIFZ OSA) ie Maes 13.4 12.8 16.5 2 9.7 
Types.—Holotype (?): Carnegie Mus. 5512; figured hypotypes: 1107902, 
110796, 117054. 
Horizon and locality—Crown Point formation on Plattsburg (15’) Quad- 
rangle in New York: On the south end of Valcour Island; in an old quarry 
just west of New York Highway 9, southwest of Bluff Point, Lake Champlain ; 
near the Normal School, 4 miles north of Plattsburg. 
