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GENUS CYPRICARDITES, Conrad; CYRTODON AND
VANUXEMIA, BILLINGS; PALAEARCA, HALL

CYPRICARDITES ROTUNDATUS, (n.s.) [vol1/38?]

Description. Shell sub-globose, height and width nearly equa
and thickness about four-fifths as great as the height from beak
to base; beaks slightly incurved, cardinal line curved, front
rounded, surface smooth or marked by obscure concentric
lines of growth. The interior of the hinge plates marked by
two lateral teeth and about four oblique cardinal teeth, Ante-
rior muscular impression of moderate size, distinct on the
anterior end.

Length three-fourths to one inch; greatest height a little
more than the length.

Geological Formation and Locality. Trenton group, (Buff
limestone), Beloit, Wisconsin.

Prof Nason, Mr. E. Hobart, T.J Hale, James Hall.

CYPRICARDITES NIOTA. (n.s.) [vol1/38?]

Description. Shell broadly sub-ovate, broadest at the poste-
rior end; umbones very gibbous; beaks incurved, little elevated,
situated about one-fourth of the length of the shell from the
anterior end. Cardinal line straight or little curved; anterior,
posterior and basal margins rounded.

Anterior muscular impression situated near to the cardinal
line, well defined; posterior imprint obscure. Surface of the
shell marked by concentric lines of growth.

This species differs from C. rotundata in being more oblique,
in the straighter cardinal line, and less ventricose form. It is
intermediate between that species and C. venntricosa, from
which it differs in the less obliquity and the greater length
from beak to base.

Length one inch and a quarter, hight one inch.

Geological Formation and Locality. In Trenton limestone,
(Buff limestone), Beloit and Chaupierre, Wisconsin.

Prof. Nason, Mr. Hobart, T.J. Hale, Jas. Hall.

CYPRICARDITES RECTIROSTRIS, (n.s.)

Description. Shell somewhat elongate-ovate, gibbous in old
specimens, young individuals moderately convex; beaks elevated,
distant, scarcely incurved; hinge line but little curved; anterior
end short, posterior end forming the greatest length of the shell;
basal margin [margin] making nearly a semicircular curve. In-