Geology and Mineralogy considered with reference to Natural Theology/Plate 39

by William Buckland

Plate 39. V. I. p. 263. Note.

This Plate presents a longitudinal view of the same fossil, of which a side view is given in the last figure. The same transverse plates that approximate so closely beneath the sides of the shell, where it is flat and feeble, (Pl. 38.) are distant from each other along the dorsal portion, which from its convex form is strong.

The Siphuncle is preserved in its proper dorsal place at d.

The elevations and depressions of the transverse plate in front of this figure exemplify the theory of Von Buch, respecting the use of the Lobes and Saddles formed by the undulations of its outer margin. See V. I. p. 267, and Note. (Original.)

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.)