REFERENCE TO THE PLATES, 
PLATE I. 
1. Ammonites giganteus, exhibiting 
the winding partitions between the 
air chambers. 
2. The lobes and sinus of a Goniatite, 
D, the dorsal region ; Z, the lateral 
region ; M, the marginal or umbi- 
lical region ; ab c, the lobes; ee e, 
the sinuses ; S, the siphuncle ; the 
barbed arrow head points towards 
the aperture, and marks the centre 
of the lobes and sinuses. See 
page 13. 
3. Nautilus Pompilius. A _ section 
exhibiting the internal structure, 
a@ a, the chambers ; 0d, the septe ; 
c, the siphuncle; A, the animal. 
See page 18. 
4. Ammonites obtusus, exhibiting the 
internal structure. From a to bis 
the portion occupied by theanimal, 
denominated the outer chamber, 
which sometimes extends as far as 
i. Theletters cd ef gh, shew the 
siphuncle, which is always situate 
in the back or ambit in the Am- 
monites. See page 14, &c. 
5. Upper view of a Rhyncholite, 
from Luneville. 
6. Goniatites Henslowi, exhibiting the 
slipper-shaped lobes on its sides. 
7. Fusus longevus, a, the apex; b, 
the base, or termination of the 
beak, in which is situate the canal ; 
c, the body ; d, the spire; eee, the 
suture of the spire ; 7, theaperture ; 
g, the inner or pillar lip; h, the 
columella ; 7, the beak, or rostrum ; 
k, the canal; 7, the front of the 
shell. 
8. A cast of a single chamber of Nau- 
tilus ziezac, shewing the deep 
curvature backwards of the two 
ventral lobes, a a. 
9. A longitudinal section of the cal- 
careous sheath and alveolus of a 
Belemnite ; a, the alveolus, or 
internal shell, divided by transverse 
septa into air chambers: b, the 
siphuncle, passing along the mar- 
gin of the air chambers; c, the apex 
of the fibro-calcareous sheath, or 
solid cone of the Belemnite. 
10. Section of an Orthocera. 
11. Portion of Ammonites yaricosus, 
shewing the transverse plates, @ 
a; and siphuncle, b. See page 5. 
12, Fusus contrarius ; a reversed shell, 
exhibiting the volutions turning in 
a contrary direction; e, a single 
volution ; d, reversed spire ; e, the 
outer lip of a reversed aperture ; 
a, the apex; b, the base of the 
beak. See page 4. 
13. Goniatites sphericus, a back view, 
shewing the lobes and saddles. 
14. Shell of the genus Littorina; a, the 
umbilicus ; c, the body, including 
the aperture; d, transverse or 
spiral ribs; b, aperture internally 
striated. 
15. A shell exhibiting a depressed spire. 
Planorbis cylindricus. 
16. A multispiral operculum. 
17. Ammonites heterophyllus; a, the 
siphuncle ; 0, the dorsal lobe; c¢, 
the dorsal saddle; d, the superior 
lateral lobe ; é, the lateral saddle ; 
J, the inferior lateral lobe; g, the 
ventral saddle : h, the ventral lobe ; 
27%, axillary lobes; k, the back, or 
ambit. 
18. Exhibits the internal volutions of 
an Ammonite (4. Murchisone,} 
enveloped by the external one; a, 
the carina or keel. See page 17. 
19. A transverse section of Goniatites 
reticulatus ; a@ and b exhibits the 
deep umbilicus on both sides, 
which is highly characteristic of 
the shells of this genus; the small 
circular mark at c shews the situa- 
tion of the siphuncle, which can 
also be seen in all the other con- 
volutions. 
20. A shell of the genus Pecten, shew- 
ing the longitudinal ribs, a a; the 
umbo, 0; the superior ear, d; the 
inferior ear, c. 
21. A shell of the genus Auricula; a, 
entire or continuous lips; 0b b b, 
the outer lip, or peritreme; c, 
og on the columella, or pillar 
ip; a, the base; d exhibits a 
transversely or spirally striated 
outer surface. 
22. A bivalve shell. The left valve; a, 
the umbo; 8, the hinge; ¢, pri- 
