40 
LITUOLATA 3 Genera. 
Shells partly spiral, the last whorl continuing in a straight line. 
Spirula.— S hell cylindrical, thin, nearly transparent, multilocular, partly turned into a 
discoidal-spiral form ; the whorls distant from each other, the last produced in 
a straight line : septa transverse, equally distant, externally concave ; syphon late- 
ral, interrupted: aperture orbicular. 
Plate XX. Fig. 7- S. Peronii. (Nautilus spirula. — Linn.) 
Spirolina. — Shell multilocular, partly discoidal-spiral, the whorls contiguous, the last 
terminating in a straight line: septa transverse, perforated by a tube. 
Plate XX. Fig. 8. S. clavata. 
Lituolites — Shell multilocular, partly turned into a discoidal-spiral form ; the whorls 
contiguous, the last terminating in a straight line: chambers irregular, septa 
transverse and simple, (without a syphon), the last perforated with from three 
to six holes. 
Plate XXII. Fig 3. L. nautiloidea. Fossil. [Icon. — Enc. Method. PI. 465, fig. 6.] 
CRISTATA. — 3 Genera. 
Shell semi-discoidal, spire eccentric. 
Renulites. — Shell reniform, flat, sulcated, multilocular; chambers linear, contiguous, 
curved about a marginal axis, the most distant from the axis the longest. 
Plate XXII. Fig. 4. R. opercularis. Fossil. [Icon. — Enc. Method. PI. 465, fig. 8.) 
Cristellaria. — Shell semi-discoidal, multilocular ; whorls contiguous, simple, progres- 
sively enlarging ; spire eccentric, sublateral : septa imperforate. 
Plate XX. Fig. 9. C. squainmula. (Nautilus planatus. — Ficlitel.) 
9 (a) Ditto magnified. 
Orbiculina. — S hell sub-discoidal, multilocular; whorls contiguous and compound; 
spire eccentric ; chambers short, very numerous ; septa imperforate. 
Plate XX. Fig. 10. O. uncinata. (Nautilus aduncus. — Fichtel.) 
10 (a) Ditto magnified. 
SPH/ERULATA — 3 Genera. 
Shell globular, spheroidal, or oval; whorls of the spire covering, or the chambers united under 
one envelope. 
Miliola. — S hell transverse, ovate-globular, or elongated, multilocular; the chambers 
transverse, surrounding the axis, alternately covering one another: aperture very 
small, situated at the base of the last whorl, either orbicular or oblong. 
Plate XX. Fig. 11. M. ovata. 
