41 
Gyrogonites. — This genus has been formed from the seed of a species of C/iara in a 
fossil state. 
Melonites. — Shell sub-spherical ; spire central ; whorls contiguous, convolute, tuniciform ; 
chambers narrow and numerous; septa imperforate. 
Plate XX. Fig. 12. M. sphseroidea. [Icon. — Enc. Method. PI. 469, fig'. g. /(.] 
12. (a) Ditto magnified. 
RADIOL AT A. — 3 Genera. 
Shell discoidal, spire central, chambers elongated, radiated, extending from the centre to the 
circumference. 
Rotalites. — 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. PI. 466, fig. 8.] 
_ • 
Lenticulites. — 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. PI. 466, fig. 5.] 
Placentula. — 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, £>.] 
13. (a) Ditto magnified. 
NAUTILACEA 6 Genera. 
Shell discoidal, spire central, the chambers short, not extending from the centre to the 
circumference. 
Discorbites.— 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. PI. 466, fig. 7, «•] 
Siderolttes. — 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, «. J.] 
8. (a) Ditto magnified. 
Polystomella. — 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. 
G 
