EXPLANATION OF THE PLATES. 37 
original specimens, it is nothing more than the terminal end ofan Orthoceras, 
such as those figured by General Portlock from the same place, as elongato- 
cinctum or subundulatum. 
Fic. 9.—THECA REVERSA, Salter. 
Siluria, second edition, p. 550. Mem. Geol. Surv. vol. iii., p. 353. 
From woodcut 14, fig. 6, p. 347. M. G.S., vol. iii. 
Caravoc.—Localities—S. of Cerrig-y-Druidion, North Wales; Bird’s Hill, 
Llandeilo, South Wales; Horderly, Shropshire; S. Scotland, M. G. S., 
vol. lii., pp. 271, 353. 
Nore.—In the List of Fossils, Appendix to Siluria, third and fourth 
editions, it is catalogued as from Llandeilo rocks only. 
CEPHALOPODA. 
Fig. 10.—ORTHOCERAS ELONGATO CINcTUM, Portlock. 
Geol. Rep. Londonderry, p. 372. 
Original. In dark grey slaty beds, Desertcreat, Tyrone, Portlock Collection. 
G&S... 
Caravoc.—Sil., fourth edition, p. 535. N. of Ireland. 
Fic. 11.—a, 6. ORTHOCERAS VAGANS, Salter. 
Journ. Geol. Soc., vol. v., pl. vi., fig. 6. M. G.S., vol. iii., p. 356. 
a, b. Original. A small example, showing septs and siphuncle (6) in lime- 
stone, from Rhiwlas, Bala. Mus. G. §S. I. 
Carapoc and LLANDOVERY.—Sil., fourth edition, p. 536. ‘ One of the very 
few Lower Silurian fossils common to the British and central European 
areas.” Localities—Rhiwlas and other localities near Bala; Coniston 
limestone of Westmoreland. M. G., vol. iii., p. 357. 
