28 CARBONIFEROUS CEPHALOPODA OF IRELAND. 



two elements of difference between these species, viz. the rate of increase and 

 the width of the intervals between the sutures. 



This may be regarded as a very rare species, only one specimen having been 

 found in the coui'se of several years of collecting. 



Remarks. — The group of forms to which Barrande' gave the name " Orthoceres 

 brevicones " are rare in the Carboniferous rocks. I am only acquainted with three 

 European species, viz. O. ilihttatuni,, de Kon.,'" 0. ciintUvs, de Kon.,^ and 0. ])<i'r- 

 ronicum, Foord. The other Carboniferous species assigned by Barrande to the 

 brevicone group prove to be species of Put er tore ra, '< ; these are " Orthoceras" 

 cordiforme, J. Sow., and "0." hitissiiiiani, Portl. The latter was even suggested 

 by its author to be " 0." cordiforme, its condition being too imperfect to admit of 

 certainty as to its true position. I shall have occasion to refer to this fragment 

 again later on. 



Fa mill/ ACTlXOCEIiATIDJE. 



Genus Actinoceras, Bronn, lS^^7. 

 AcTiNOCEEAS GiGANTEDM, /. Sowerhij, sp. Plate IX, figs. 2 a — c. 



1821. Oethoceea gigantea, J. Sowerbi/. Miu. Conch., vol. iii, p. 81, pi. ccxlvi. 

 1836. OETnocERAS giganteusi, J. Phillips. Geol. of Yorkshire, pt. 2, p. 237, 



pi. xxi, fig. 3. 

 1840. AcTiNocEHAs SiiiMSii, C. Stokes. Trans. Geol. Soc, ser. 2, vol. v, pt. 3, 



p. 708, pi. lis, figs, -i, 5. 



1843. — — J. U. Portlock. Eep. on the Geol. of Londonderry, 



&c., p. 391. 



1844. Oethocehas giganteum, L. G. de Koninck. Descriji. Anini. Foss. Belg., 



p. 510, pi. sliv, fig. 2 ; pi. xlv, fig. 3 ; pi. slvi, 



and pi. xlvii, fig. 1. 

 1844. AcTiNocEiiAs GIGANTEUM, F. AL'Coy. Synop. Carb. Foss. Ireland, p. 11. 

 1844. — PYBAMIDATUM, F. M'Cuy. Ibid., p. 11, pi. i, fig. 5. 



1854. — oigaxteum, F. A. Roemer. Beitr. z. geol. Kenntu. des 



nordwest. Harzgeb., Palseontographica, Band 

 iii, p. 93, pi. siii, figs. 27 a — c. 



1855. Oethoceeas (Actinoceras) giganteum, F. M'Coy. British Pal. Foss., 



fasc. 3, p. 571. 

 1862. Actijjoceeas giganteum, E. Grijith. Journ. Geol. Soc. Dublin, vol. ix, 



pp. 33 and 55. 

 1874. — — J. Younrj and J. Armsirotuj. Trans. Geol. Soc. 



Glasgow, vol. iv, p. 280. 



' ' Syst. Sil. de ia Bohcme,' vol. ii, p. 18. 



2 ' Descrip. Aaiai. Foss. Belg.,' 1842-4, p. 515, pi. xlv, figs. 8, 9. 



» Idem, Suppl., 1851, p. 54, pi. lix, fig. 1. 



