22 
SECTION III. 
Either no ligament, or none knonn; or represented by a tendinous cord, which supports the shell. 
Tuis Section contains Two Families— Rudista, and Brachiopoda. 
RUDISTA.—6 Genera. 
Ligament, hinge, and animal unknonn; shell very inequivalve. No distinct beaks. 
SPHERULITES.—Shell inequivalve, orbicular-globose, rather depressed above, echinated 
externally with large, subangular, horizontal scales; upper valve smallest, rather 
flat, opercular; the internal surface furnished with two unequal, subconical, curv- 
ed, and prominent tuberosities; lower valve largest, rather ventricose, the exter- 
nal margin radiated with scales; cavity obliquely conical, and forming on one side, 
by the folding of the internal margin, a crest, or projecting keel: internal side of 
the cavity transversely striated. Hinge unknown. 
Plate XXI. Fig. 6. S. foliacea. Fossil. [Icon.—Encyc. Method. pl. 172. fig. 7.] 
Rapviottrrs.—Shell inequivalve, externally striated; the striae longitudinal, radiating : 
lower valve turbinated, and largest; the upper, convex or depressed conical, oper- 
cular. Hinge unknown. 
Plate XXI. Fig. 7. R. turbinata. [British Museum.] 
CacroLa.—Shell inequivalve, triangular, turbinated, flattened beneath; the larger valve 
hollowed or hood-shaped, obliquely truncated at the aperture; the cardinal mar- 
gin straight, transverse, a small notch or indentation in the middle; the superior 
margin arched: the small valve flat, semi-orbicular, opercular, having a tubercle 
on each side of the cardinal margin, and, in the middle, a pit with a small lamina. 
Plate XXI. Fig. 8. C. sandalina. [Mr.J.D.C.Sowerby’s Cabinet. ] 
Brrostrites.—Shell inequivalve, bicornute, the disk of the valves-elevated conically, un- 
equal, obliquely diverging, nearly straight, horn-shaped, the one enveloping the 
other at the base. 
Plate XXI. Fig. 9. B. inequiloba, [Mr.J. D.C. Sowerby’s Cabinet.] 
Discrna. 
Shell inequivalve, oval-rotundate, rather depressed, valves nearly equal, each 
having an orbicular disk in the centre, very distinct; disk in the upper valve not 
perforated, with a mammillated protuberance in the middle; that in the other valve 
very white, divided by a small transverse slit. 
Plate XIII. Fig. 2. D. Norvegica. (Orbicula Norvegica.—Sowerby’s Genera.) [Mr. G. B. Sower- 
(a) Lower valve of ditto. by’s Cabinet. ] 
(b) Upper valve of ditto. 
CraniA.—Shell inequivalve, suborbicular, lower valve almost flat, perforated in the in- 
ternal surface by three unequal and oblique holes; the upper valve very convex, 
furnished interiorly with two prominent callosities. 
Plate XIII. Fig. 3. C. personata. (Anomia craniolaris.— Linn.) 
(a) Lower valve of ditto. 
(b) Upper valve of ditto, 
