41 
GyroconitEs.—This genus has been formed from the seed of a species of Chara ina 
fossil state. 
Me onitEs.—Shell sub-spherical ; spire central; whorls contiguous, conyolute, tuniciform; 
chambers narrow and numerous; septa imperforate. 
Plate XX. Fig. 12. M. sphzroidea. [{Icon.—Enc. Method. P1. 469, fig. g. h.] 
12. (a) Ditto magnified. 
RADIOLATA. —3 Genera. 
Shell discoidal, spire central, chambers elongated, radiated, extending from the centre to the 
circumference. 
Rora.ites.—Shell orbicular, spiral, convex or conoidal above, flattened, radiated, and 
tuberculated beneath, multilocular: aperture marginal, triangular. 
Plate XXII. Fig. 5. R. trochidiformis. Fossil. [Icon.—Enc. Method. Pl. 466, fig.8.] 
Lenticutites.—Shell sub-lenticular, spiral, multilocular; the external margin of the 
whorls folded in two, extending above and below, even with the centre of the shell: 
septa entire, curved, the two sides prolonged in form of rays: aperture narrow, 
projecting over the penultimate whorl. 
Plate XXII. Fig. 6. L. rotulata. Fossil. [Icon—Enc. Method. Pl. 466, fig.5.] 
PLacentTuLa.—Shell orbicular, convex above and beneath, multilocular: aperture oblong, 
narrow, formed like a ray on the lower, or on both disks 
Plate XX. Fig. 13. P. asterisans. [Icon.—Enc. Method. Pi. 466, fig. 10, b.] 
13. (a) Ditto magnified. 
NAUTILACEA.—6 Genera. 
Shell discoidal, spire central, the chambers short, not extending from the centre to the 
circumference. 
Discorsitres.—Shell discoidal, spiral, multilocular, sides simple: the whole of the whorls 
apparent, naked, and contiguous to one another; septa transverse, frequent, not 
perforated. 
Plate XXII. Fig. 7. D. vesicularis. Fossil. [Icon.—Enc. Method. Pl. 466, fig. 7, a.] 
SripERoLITES.—Shell multilocular, discoidal; whorls contiguous, not apparent outside ; disk 
convex on both sides, and studded with tubercles, with unequal and radiated 
lobes on the periphery: septa transverse and imperforate; aperture distinct, 
sublateral. 
Plate XXII. Fig 8. S. calcitrapoides. Fossil. [Icon—Enc. Method. PI. 470, fig. 4, a. 6-] 
8. (a) Ditto magnified. 
PotystoMELLA.—Shell discoidal, multilocular; whorls contiguous, not visible exter- 
nally; the exterior radiated by transverse furrows or ribs: aperture composed of 
many holes variously disposed. 
Plate XX. Fig. 14. P. crispa. 
14. (a) Ditto magnified. 
