66 
EXPLANATION OF PLATE 44'. 
Fig. 15. Scaphites Equalis, from Chalk near Rouen, in 
the collection of Mr. J. Sowerby; the sides of the 
external shell are strengthened and ornamented by 
ribs and tubercles ; and the edges of the transverse 
plates disposed in sinuous foliations (c.) as in Am- 
monites. The mouth or outer margin ( 5 .) returns so 
nearly into contact with the air chambers (c.), that 
the want of space at this part for the expansion of 
arms and head, makes it probable that the Scaphite 
was placed entirely within the body of its animal. 
(Original.) 
Fig. 16. Transverse section of the chambered portion of 
Fig. 15, shewing the arrangement of the lobes and 
saddles to be similar to that of Ammonites; the 
siph uncle also is seen on the dorsal margin at a. 
(Original.) 
Fig. 17. Longitudinal section of the calcareous Sheath 
and Alveolus of a Belemnite. 
a. Alveolus, or internal shell, divided by transverse 
Septa into air chambers. See V. I. p. 373 ^ 
b. Siphuncle, passing along the margin of the air cham- 
bers. 
c. Apex of the fibro-calcareous sheath, or solid Cone of 
the Belemnite. 
Elate 44'. 
V. 1. p. 371, et seq. 
Illustrations of the probable nature of the Animals that 
gave origin to Belemnites.* 
» In the descriptions of PI. 44'. and PL 44". the folloiving letters 
indicate the same parts in each specimen to which they are applied. 
a. The Apex of the calcareous shell, or sheath. 
h. Alveolar portion, or chambered shell. 
c. Ink-bag. 
rf.> Portions of the thin anterior horny sheath, sometimes highly 
€. ) nacreous, 
y. Neck of Ink-bag. 
