BRACHIOPODA. 
179 
there is danger of confounding it, by the convex pedicle-valve, the distant, 
elevated, concentric surface-ridges, which have a peculiar undulation as they 
approach the margins of the foramen. The internal characters of the shell are 
at once distinctive. (See discussion of these features on page 134.) Length 
and width of a mature specimen, 50 mm. 
Hamilton group. Leonardsville, Hamilton , Darien and Canandaigua Lake , 
N. Y. 
SCHIZOCRANIA SCHUCHERTI, Sp. nOV. 
PLATE IV G, FIGS. 31-33. 
Shell small, usually found unattached; marginal outline subovate. Surface 
of pedicle-valve flat or slightly concave; concentrically striated. Pedicle- 
aperture broad and sharply triangular. Brachial or upper valve strongly 
convex, often laterally compressed. Umbo full and rotund, incurved at the 
apex, which is almost, but not quite marginal. Surface covered by numerous 
simple, sharply elevated, uninterrupted strim, frequently crossed by concen¬ 
tric wrinkles. On the interior of this valve only the strong posterior 
muscular impressions are distinctly shown. 
Hudson River group. Cincinnati, Ohio. 
Schizocrania (?) Helderbergia, sp. nov. 
PLATE IV G, FIGS. 34, 35. 
Shell subcircular in outline. Upper valve convex; apex posterior and mar¬ 
ginal. Surface covered with fine, closely crowded, elevated, radiating lines, 
which extend to the apex, and increase by intercalation. Lower valve flat 
and of less diameter than the upper. Apex subcentral, posterior. Foramen 
apparently a narrow triangular slit extending to the margin. A short median 
septum extends forward from the apex. External surface covered with low, 
crowded and rather faint concentric lines. On the interior, the surface bears 
a series of distant, deep but narrow radiating furrows, about twenty-five in 
number; these do not reach the apex, and increase in number toward the 
margin. Between them are very fine radiating lines. The animal was para- 
