36 EXPLANATION OF THE PLATES, 
b. Original. Enlarged outline, showing arrangement of hinge teeth. 
Caravoc.—Locality, W. of Bala Lake, Merionethshire. M. G.S., vol. iii., 
p. 270, and County Tyrone. 
GASTEROPODA. 
Fie. 5.—HoLorEa CONCINNA, DM‘ Coy, sp. 
? Naticopsis, Sil. Foss. Irel., p. 13. Holopea, Cat. Brit. Foss., 1854, p. 
252. 
Original. In grey and red Lower Silurian limestone; Chair of Kildare, 
Treland. Mus. G. S. I. 
Carapoc.—Very abundant in the limestone of the Chair of Kildare ; it also 
occurs in dark grey limestone of corresponding age at Portraine, Co. Dub- 
lin; and at localities in Denbighshire and Merionethshire, N. Wales. M. 
G. S., vol. i., p. 271. 
Fic. 6.—a, b. Murcuisonia turR1TA, Portlock, sp. 
Pleurotomaria, Geol. Rep. Londonderry, &c., p. 4138. Murchisonia, Sil., 
fourth edition, p. 532. 
a,b. Original. Front and back view of the same shell. In dark grey slaty 
beds, Desertcreat, Tyrone. Portlock Collection, Mus. G. 8. I. 
Carapoc.—County Tyrone, N. of Ireland. It is also included in the list of 
Caradoc fossils (on the authority of Professor M‘Coy), as occurring at Bala, 
Merionethshire. M. G.S&%., vol. iii., p. 271. 
HETEROPODA. 
Fic. 7.—a, b. BELLEROPHON BILOBATUS, Sowerby. 
Sil. Syst., p. 643. B. bilobatus, elongatus, and gibbus, Geol. Rep. London- 
derry, pp. 397-8. Cat. Brit. Foss., p. 287. 
a, b. Front and side view. From Sil. Syst. pl. xix., fig. 13. 
LLANDEILO To LLANDOVERY.—Sil., fourth edition, p. 533. ‘ One of the 
common fossils of the lower part of the Caradoc sandstone, and equally 
characteristic of the same deposits in North America, Spain, and Bohemia.” 
Ibid., p. 198. Localities, Horderly in Caradoc sandstone, also Llandeilo 
flags, N. Wales. Ibid. explanation to pl. vii., fig. 9. N. and S. Wales in 
Upper Llandeilo Rocks, M. G. S., vol. iii., p. 259; and in Caradoc rocks 
at several localities in N. Wales, ibid. p. 271. In Ireland it is abundant 
in rocks of the same age at Desertcreat, Tyrone, and in the counties of 
Wexford and Waterford. 
PTEROPODA. 
Fic. 8.—? THECA TRIANGULARIS, Portlock, sp. 
? Orthoceras, Geol. Rep. Londonderry, p. 375. Theca, Cat. Brit. Foss. p. 
232. 
Original. In dark grey slaty beds, Desertcreat, Tyrone. Portlock Collec- 
tion, Mus. G. S. I. 
Carapoc.—Localities—S. of Cerrig-y-Druidion, Denbighshire. M. G.S&%., 
vol. ili., p. 271. 
Nore.—I have figured this fossil as a Theca on the authorities above- 
mentioned, although { am inclined to think, on further examination of the 
