( 18 ) (Orthoceracee.) 
a, Contractions moderate. Pl. 2, fig. 9. 
6. Contractions so deep that the septa are united by the siphon only and ap- 
pear as if strung together. Pl. 2, fig. 12. 
6. Hreruritrs. Lam. Cor- 
nu-cop1z. Thomson. 
Thick, cylindrical or A siphon, agutter in- Several large species 
conical, with irregular sep-° steadofasiphon,orboth. in the older Secondary 
ta traversing two longitu- Mountains. 
dinal cylindrical projec- 
tions adhering to one of 
the sides; mouth closed 
by an operculum. Pl. 4, 
fig. 21, 26, 28, 34,33. Pl. 
2, fig. 18. 
ae Conical, more or less arched. Pl. 4, fig, 21. 
6. Batholites, Montf. Straight, cylindrical. 
7. Bacusites. Faujas. Ha- 
mites. Parkinson. 
Straight, cylindrical, a Maestricht. In the ~ 
litttle conical, fusiform, clay at Folkstone. In 
hooked or bent, com- the chalk at Hamsey and 
pressed : septa transverse, at Horton. 
undulated at the mar- 
gins. Pl. 4, fig. 17, 19. 
PLA? thie. 10s) PI. 3) fig. 
48, 23. 
a, With a siphon at the outer edge of the chambers. 
6. Without oe oe ee 
8. ‘Turaiwites. Montf. 
Spiral, turreted; with — Septa pierced in their — St. Catherine’s Mount 
chambers divided by si- disks. near Rouen. In the 
nuous septa: the turns green sand at Horning- 
contiguous, all visible : sham, Wilts. Hamsey 
mouth round. Pl. 4, fig. Marl Pit. 
16. 
Belemnites. 
According to M. Beudant, they have never been found in transition limestone, 
or grey wacke, but first appear in the argillaccous iron stone which alternates with 
bituminous slate. The internal of the two testaceous cones is filled with a solid 
substance, presenting either radiating fibres or conical beds enveloping each other, 
and their bases corresponding with the edges of the septa of the interior cone: 
this solid part is sometimes found alone ; at others, the kernels of the chambers of 
the interior cone or the alveoliare also met with. P1.1, fig.9. Most frequently the al- 
veoliand the chambers themselves have left no other traces than some projecting cir- 
cles within the interior cone; but we sometimes meet with the alveoli still piled on 
one another, but detached from the double conical case which envelopes them. 
The exterior cone has generally a notch on one side of the base continued in a longitu- 
dinal furrow. Klein, in 41734, was the first who considered the fusiform Belemnites to 
be spines of Echini, from the similar exterior form, and the radiation presented in 
