308 PALEOZOIC PALEONTOLOGY. 
SCENIDIUM INSIGNE (Hall). 
Plate XXXVI., Figs: 1-4. 
1859. Orthis insignis Hall, Pal. N. Y., vol. III., p. 173, pl. 18, figs. 
135-16. 
Description.—Shell minute, subpyramidal in form, greatest width 
along the hinge-line. Pedicle valve with an extremely-elevated, 
pointed, straight or slightly-incurved beak, cardinal area large, flat 
or slightly concave, delthyrium broadly triangular, mesial line slightly 
elevated in a low, narrow, rounded fold, from which the sides slope 
away to the cardinal and lateral margins. Brachial valve semi-cir- 
cular, nearly flat, with a well-marked sinus along the mesial line. 
Surface of each valve marked by from five to seven flat, rounded 
plications on each side of the fold and sinus. 
The dimensions of a full-grown specimen are, approximately: 
length, 2 mm.; width, 4 mm.; height of area on pedicle valve, 2 mm. 
Remarks.—This minute species is occasionally detected upon the 
weathered surfaces of the cherty limestone at the base of the New 
Scotland beds. 
UNCINULUS VELLICATUS (Hall). 
Plate XXXVI., Figs. 5-7. 
1859. Rhynchonella vellicata Hall, Pal. N. Y., vol. III., p. 230, pl. 
33, figs. 1 a—p. 
Description—Shell subovate to subrhomboidal in outline, wider 
than long. Pedicle valve convex on the umbo, the cardinal and lateral 
margins inflected, depressed toward the front along the median por- 
tion of the shell in a rather broad and shallow sinus, which is pro- 
duced anteriorly; beak rather inconspicuous, closely incurved over 
that of the opposite valve. Brachial valve much more convex than 
the pedicle, most prominent in front, with a rather ill-defined mesial 
fold, reaching from the middle of the shell to the anterior margin. 
Surface of each valve marked by from twenty-four to thirty-four low, 
rounded plications, which continue to the beak. On the pedicle valve 
