Lign. 137.
Murchisonia angulata.
Devonian; Eifel.
Murchisonia. [Lign. 137]. An elongated spiral shell, having the outer lip deeply notched, as in the Pleurotomaria ([a, Lign. 137]). There are upwards of 50 species of this genus, which are characteristic of the palæozoic rocks. They occur in the Permian, Devonian, and Lower Silurian deposits; the specimen figured is from the Devonian, or Old Red of the Eifel.
Chiton. Valves of Chitons have been found in the Magnesian limestone, near Sunderland, by Prof. King, (Permian Fossils, Pal. Soc. p. 202, pl. xvi.), and in the Silurian rocks of Ireland, by Mr. Salter, Geol. Journal, vol. iii. p. 48.
SPHÆRULITES.
Sphærulites.[388] [Lign. 138.]—No vestiges of a shell of this genus had been noticed in the English strata, until my discovery of some fragments in the Lewes Chalk in 1820; from the lamellated structure of these fossils, I mistook them for corals, until specimens were obtained sufficiently perfect to show the form of the originals; these were described in the Geol. S. E. (p. 130), under the name of Hippurites. But these fossils are more nearly related to the Sphærulites, which differ from the shells of the former genus in having only one internal longitudinal ridge, and in the external surface being roughened by irregularly raised plates, as in [Lign. 138, fig. 1], which is a specimen from the Pyrenees, collected by M. Alex. Brongniart; the operculum is seen at a.
[388] This genus has been referred by some conchologists to the Bivalves, and by others to the Univalves.
Lign. 138. Sphærulites from the Chalk of France and England.
| Fig. | 1.— | Sphærulite, with its operculum, a. |
| 2.— | Sphærulites Mortoni (G. A. M.), from Lewes: 1/2 nat. | |
| 2a.— | Cellular structure of fig. 2, in a transverse section: × | |
| 2b.— | Structure, as seen in a vertical section: × |