506 PALEOZOIC PALEONTOLOGY. 
DALMANELLA SUBCARINATA (Hall). 
Plate XXXIV., Figs. 10—13. 
See, also, p. 326. 
1859. Orthis subcarinata Hall, Pal. N. Y., vol. IIL., p. 169, pl. 22; 
figs. 7-21. 
Description.—Shell subplano-convex in form, subcircular, subquad- 
rangular or transversely subelliptical in outline, the hinge-line one- 
half to two-thirds the greatest width. Pedicle valve strongly convex, 
subearinate along the median line, sloping to the lateral margins; 
beak small, incurved over the narrow area. Brachial valve more or 
less flattened, with a distinct depression along the median line, which 
becomes wider anteriorly, producing a sinus in the front margin of 
the shell. Surface marked by fine, raised, equal or alternating stri, 
which increase by irregular bifurcation and are curved towards the 
cardinal margin; marked, also, by finer, concentric striz over the 
entire surface and by strong lines of growth toward the margin of 
adult shells. 
The dimensions of an adult specimen of average size are: length, 17 
mm.; width, 18 mm.; convexity of pedicle valve, 6 mm. 
Remarks.—This shell resembles D. perelegans, and it is probable 
that the two species run together. In its typical form it differs from 
the last in being more nearly plano-convex and usually in being some- 
what smaller. 
BILOBITES VARICA (Con.). 
Plate XXXV., Figs. 14—18. 
1859. Orthis varica Hall, Pal. N. Y., vol. IL, p. 179, pl. 24, figs. 
la-k. 
Description.—Shell small, subcordate in outline, deeply bilobed in 
front, with a deep sinus in each valve; hinge-line from one-third to 
one-half the greatest width. Pedicle valve the most convex, with a 
somewhat deeper and sharper sinus; the beak pointed, slightly in- 
eurved over the rather high, concave, cardinal area; delthyrium 
