CORALS FROM THE SILURIAN FORMATION. 253 



same genus. In most other respects H. Grayi much resembles H. Murchisoni 1 and H. 

 inordinata? but may be distinguished from both by the circular exsert margin of the 

 calices. 



The fossil figured in M. Murchison's justly-celebrated work under the name of 

 Bloienbachium globosum Lonsdale, 3 appears to be a mould of a coral belonging to the 

 above-described species. It was found at Wenlock. 



5. Heliolites inordinata. Tab. LVII, figs. 7, la. 



Porites inordinata, Lonsdale, in Murchison, Silur. Syst., p. 687, pi. xvi bis, fig. 12, 1839. 

 Lonsdalia inordinata, I? Orbigny, Prodr. de Pale'ont., vol. i, p. 25, 1850. 

 Pal.eopora subtilis? M'Coy, Brit. Palaeoz. Foss., p. 17, 1851. 



Heliolites inordinata, Milne Edwards and Jules Haime, Pol. Foss. des Terr. Palaeoz. 



(Arch, du Mus., vol. v), p. 217, 1851. 



Corallum arborescent, very ramous ; its branches slender, subcylindrical, and about one 

 or one and a half line in diameter. Calices not prominent, circular, or somewhat elongated 

 in the longitudinal direction of the branches, and set at various distances from each other 

 in different part 1 ? of the corallum. Septa 12 in number, nearly similar in size, rather thick, 

 and well developed. Cells of the ccenenchyma polygonal and somewhat irregular. 

 Diameter of the calices about half a line. 



Found in the lower Silurian beds at Robeston Walthen, Pembrokeshire. According 

 to Professor M'Coy it exists also in the upper Silurian deposits at Ferriter's Cove, 

 Doonquin, and Dingle, in Kerry. The fossil which Professor M'Coy describes under the 

 name of Palaopora subtilis, 1 and which (from the description given by that author) we are 

 inclined to consider as not differing specifically from H. inordinata, appears to be common 

 in the fine Caradoc sandstone of Mulock, Dalquorhan, Ayrshire. Specimens are in the 

 Collection of the Geological Society. 



The above-described species differs from the other Heliolites by its dendroidal form, 

 and by the development of its septa. 



2. Genus Plasmopora, (p. lix.) 



1 Plasmopora petalipormis. Tab. LIX, figs. 1, la, Id, Ic. 



Porites petaliformis, Lonsdale, in Murchison, Silur. Syst., p. 687, pi. xvi, fig. 4, 1839. 

 Astreopora petaltformis, U Orbigny, Prodr. de Paleont., vol. i, p. 50, 1850. 

 Pal/EOPOra petaliformis, M'Coy, Brit. Palaeoz. Foss., p. 17, 1851. 



Plasmopora petaliformis, Milne Edwards and Jxdes Haime (Introd., p. lix, 1850), 



Polyp. Foss. des Terr. Palaeoz., p. 221, 1851. 



1 See tab. lvii, fig. 6. 2 See tab. lvii, fig. 7. 3 Silurian System, tab. xv, fig. 26. 



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