42 
VorticraALis.—Shell discoidal, spiral, multilocular ; whorls contiguous, not apparent out- 
wardly; septa transverse, imperforate, not extending from the centre to the peri- 
phery: aperture marginal. 
Plate XX. Fig. 15. V. strigilata. [Icon.—Enc. Method. PI. 470, fig. 2, a. b.] 
15. (a) Ditto magnified. 
Nummutites.—Shell lenticular, thin towards the margins; spire internal, discoidal, mul- 
tilocular, covered by many thin plates; exterior margin of the whorls folded in two, 
extending from each side of the shell to the centre, and uniting: chambers very 
numerous, small, alternate; septa transverse, imperforate. 
Plate XXII. Fig. 9. N. complanata. Fossil. [Mr. J. D. C. Sowerby’s Cabinet. ] 
Navtitus.—Shell discoidal, spiral, multilocular, sides simple; whorls contiguous, 
the last covering the others. Chambers numerous; septa transverse, concave 
from the side of the aperture; disk perforated by a tube; and the margins very 
simple. 
Plate XX. Fig. 16. N. umbilicatus. 
II.— Shell multilocular, the septa indented at the borders. 
AMMONEATA.—5 Genera. 
Septa sinuous, lobed, and indented at the cirewmference, wnited at the inner surface of the shell, and 
articulating mith it by means of indented sutures. 
AmmoniTEs.—Shell discoidal, spiral; the whorls contiguous, and the whole of them ap- 
parent; the internal partitions articulated by sinuous sutures: septa transverse, 
lobed and indented at the circumference, their diskswithout a syphon, but pierced 
by a sort of marginal tube. 
Plate XXII. Fig. 10. A. armatus. Fossil. (Sowerby’s Min. Conch.) [Mr. G. B. Sowerby’s Cabinet. ] 
OrsutitEes.—Shell sub-discoidal, spiral; the whorls contiguous, the last covering the 
others, and the internal partitions articulated by sinuous sutures: septa trans- 
verse, lobed at the circumference, and perforated by a marginal tube. 
Plate XXII. Fig. 11. O. striata. Fossil. [British Museum.] 
AmmonocrraTiTEs.—Shell corniform, arched, semicircular; partitions articulated by si- 
nuous, ramose, indented sutures: septa transverse, sinuous, lobed and indented at 
the circumference. Tube or syphon marginal, not piercing the septa. 
Plate XXII. Fig 12. A. glossoidea. Fossil. {Icon.—Bowdich’s Elements of Conc.] 
Turriites.—Shell spiral, turreted, multilocular; the whorls contiguous, and the whole 
apparent; the partitions articulated by sinuous sutures: septa transverse, lobed, 
and indented at the circumference. Aperture rounded. 
Plate XXII. Fig. 13. T. costulata. Fossil. [Mr. G. B. Sowerby’s Cabinet.) 
