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16 BRITISH PALAEOZOIC FOSSILS. [ZoOPHYTA. less than three and often five between each of the cell-tubes). Mr Lonsdale’s reference (Sil. Syst.) of this coral to the Devonian P. pyriformis (Blainv.) is universally admitted to be injudicious. The two specific names above quoted from M. d’Orbigny, are merely given as names to the separate figures of this species in the Silurian System, without definitions; and I believe there is no specific distinction to be drawn between them. Position and Locality.—Abundant in the Wenlock limestone near Aymestry, Herefordshire; calcareous shales, Wenlock, Shropshire; Malverns; Coniston limestone of Long Sleddale, Westmoreland. A doubtful variety rare in Coniston limestone at Coniston Water-Head, Lancashire, and in the impure calcareous schists of Applethwaite Common, Westmoreland. Yar. a. subtubulata (M r Coy). PI. 1. C. fig. 2. S'p. Cli.—Corallum composed of radiating thick-walled persistent cylindrical tubes (often exhibited separately in the weathered vertical section), with the usual diameter of half a line, generally more than their diameter apart, crenulations and radiating lamellae very small and indistinctly marked; horizontal diaphragms strong, flat, two interdiaphragmatae equal to the diameter of the tube; interstitial spaces filled with very numerous, minute, capillary, polygonal tubes, the spaces between the diaphragms of which are slightly less than their diameters. In the frequency with which the cylindrical tubes are exhibited in weathered specimens distinctly separated from the mass, as well as the distance of the diaphragms apart, this species resembles the P. tululata (Lonsd. Sp ), from which it is distinguished by the distance of the tubes apart, the nearly obsolete crenulations or radiation of their interior, and by the intervening space being filled with very numerous capillary prismatic tubes; in the last two characters it approximates to the P. interstincta, from which it is distinguished by the greater strength of the walls of the tubes, their small diameter and greater distance from each other, and more distant diaphragms; but as I have noted a small-tubed variety of the P. interstincta from Malvern, apparently in some degree intermediate, I only propose this at present as a strongly-marked variety of that species. Position and Locality.—Occurs occasionally in the Coniston limestone of Coniston Water-Head, Lan cashire, and Llansantfraid, Denbighshire; Wenlock limestone, near Aymestry, Herefordshire. Explanation of Figures.—Plate 1. C. fig. 2. Portion of weathered mass, natural size, from Coniston Water, shewing the main tubes projecting in one part.—Fig. 2 a. Portion of ditto magnified six diameters, shewing the weathered appearance of the base of the lamelliferous tubes and the interstitial tubules.— Fig. 21. Portion of weathered mass magnified six diameters, shewing the projecting lamelliferous tubes, and intervening polygonal tubuli. PALiEOPORA MEGASTOMA (M c Coi/). PI. 1. C. fig. 4. Ref. and Syn.—Porites megastoma (M'Coy). Syn. Sil. Fos. of Ireland, t. 4. f. 14. Sp. Ch.—Corallum forming large hemispherical or irregular masses; base concentrically rugose; stellular tubes averaging a line and half in diameter, with strong radiating lamell e about one-fourth the diameter of the tube in length; diaphragms strong, apparently pitted on their upper surface; interstices of small polygonal vertical tubes, (averaging five in one line) ; usually about three interstitial tubes in a line between the lamelliferous tubes, which are in most cases rather less than half their diameter apart. This species seems to replace in abundance, in the lower Silurian beds, the so-called P. pyriformis (P. interstincta) of the Wenlock Rocks. It is distinguished from that species by the great size of the stel lular tubes, which vary in the adult from one and half to nearly two lines in diameter, and the great proportional strength of the walls, which frequently causes them, like P. tululata, to stand up as separate sulcated columns in the weathered examples; the radiating lamellae are also much more strongly marked in the P. megastoma, which serves to distinguish the dwarf examples in which the tubes may occasionally sink to near the same diameter; the transverse diaphragms seem irregularly pitted on their upper surface and to be smooth below.