Geology and Mineralogy considered with reference to Natural Theology/Plate 40
Plate 40. V. I. p. 272. Note.
Fig. 1. Ammonites Henslowi (Goniatites,) from Transition limestone in the Isle of Man.
The Lobes are simple, and without foliations; their form resembles that of the slipper-shaped lobe of the Nautilus Ziczac, and Nautilus Sypho. See Pl. 43.
The lobes D. L. l. V. are pointed inwards, and the intermediate Saddles S. d. S. L. S. V. are rounded outwards; according to the type of Ammonites. (Original.)
Fig. 2. Ammonites striatus (Goniatites,) from the Coal Shale of Lough Allen in Connaught, having its lobes and saddles disposed in the same directions as in Fig. 3, the delicate longitudinal striæ and transverse ribs of the outer shell are strengthened by repeated intersections of the subjacent edges of the transverse Plates. (Original.)
Fig. 3. Back view of Ammonites sphæricus, from the limestone of Derbyshire, showing the position of the siphuncle upon the dorsal margin, with its collar advancing outwards between the two simple dorsal lobes; the lateral lobes are also simple and without foliations, and pointed inwards. (Martin Pet. Der. T. 7.)
Fig. 4. Ammonites nodosus (Ceratites). This is one of the species peculiar to the Muschel-kalk. The descending lobes terminate in a few small denticulations, pointed inwards, and the ascending saddles are rounded outwards, after the normal character of Ammonites. (Zeiten. Tab. II. Fig. 1. a.)
Fig. 5. Back of A. Nodosus, showing the dorsal lobes pointed inwards, and the collar around the siphuncle advancing outwards. No edges of the transverse plates are placed beneath the dome-shaped Tubercles; these derive sufficient strength from their vaulted form. (Zeiten. Tab. II. Fig. 1. b.)