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CONCHIFERA. 
Genus 5.' —DISCINA.— Lamarch. 
Generic Character. —Inequivalve, of a rounded oval shape, 
and depressed; valves equal in size, each provided with an or¬ 
bicular and central disk; that of the upper valve not perforated, 
but having a mammillated projection in the centre; the lower 
valve divided by an oblong fissure. 
Discina ostreoides. — The Oyster-like Discina. 
Plate LXXXVII. fig. 8. a, the upper valve; b, the under valve. 
Upper valve longitudinally ribbed, crossed by concentric strite. 
Five lines long. Inhabits the Zetland seas. 
Genus 6.—BIROSTRITES.— Lamarch. 
Generic Character. —Inequivalve, with two horns; the disks 
of the valves elevated, conical, and unequal, oblique, diverging, 
and sub-erect, somewhat horn-shaped; the one valve enveloping 
the other at the base. Fossil. 
Genus 7. — CAL CEO LA.— Lamarck. 
Generic Character. —Inequivalve, triangular, turbinated, flat¬ 
tened beneath; the larger valve hollowed like a hood, and trun¬ 
cated obliquely at the aperture; the smaller valve somewhat 
orbicular, and in the form of a lid, having a furrow in the centre. 
Fossil. 
Genus 8. — RADIOLITES.— Lamarck. 
Generic Character. —Inequivalve, and interiorly striated, ra¬ 
diating from the umbo ; lower valve turbinated, and the largest; 
the upper one convex or conical, and lid-shaped. Fossil. 
Genus 9. — S PII M R ULITE S— Lamarck. 
Generic Character. —Inequivalve, suborbicular-globose, some¬ 
what depressed above, roughened with large subangular horizon¬ 
tal scales; the upper valve the least, flattened, lid-shaped, with 
two unequal tubercles within; under valve subventricose, with 
the scales radiating beyond the margin, and forming a ridge; 
inside partly striated ; hinge unknown. 
Section II. — Ligament not marginal, enclosed in a short 
