CORALS FROM THE SILURIAN FORMATION. 293 



8. Genus Strombodes (p. lxx). 



i. Strombodes typus. Tab. LXXI. figs. 1, la, \b. 



Arachnophyllum typus, M'Coy, Ann. and Mag. of Nat. Hist., 2d ser., vol. vi, p. 278, 1850. 



_ _ M'Coy, Brit. Paheoz. Foss., p. 38, pi. i B, fig. 27, 1851. 



Strombodes Labechii, Milne Edwards and Jules Haime, Pol. Foss. des Terr. Palseoz. 



(Arch, du Mus., vol. v), p. 427, 1851. 



Corallum composite, massive, sub turbinate ; its upper surface slightly convex ; its basal 

 common plate covered with a very thin epitheca, and presenting very prominent and 

 irregular accretion ridges. The terminal surface of the corallites irregularly polygonal, and 

 separated from each other by strong ridges that are more prominent at their angles than 

 elsewhere. Near the centre of these polygonal spaces a slight circular elevation, corres- 

 ponding to the upper edge of the inner wall, and circumscribing the true calice. Septal radii 

 not distinct from the costas, and thus extending to the outer edge of the corallite. The total 

 number of the septo-costal radii amounts to about 100, but one third of them only extend 

 to the calicinal fossula, where they become curved and somewhat prominent : most of them 

 appear to bear small paliform lobules. The marginal or costal radii are still slenderer than the 

 preceding ones, and adhere to them at their inner edge. Very slender, closely set, unequally dis- 

 tinct dissepiments unite all these radii, so as to constitute delicate very regular quadrangular 

 reticulations. Vertical and horizontal sections show that the structure of the corallum is 

 essentially vesicular. In a section corresponding to the direction of the axis of the corallites, 

 the different layers of that vesicular tissue being of different degrees of density, constitute 

 undulated parallel horizontal lines, the direction of which correspond to that of the surface 

 of the corallum. A horizontal section shows that the inner or true walls are circular 

 and well constituted, and that the reticulations become larger and more regular towards 

 the circumference of the corallites. In many parts no remains of the costse septal radii are 

 distinct, and the space comprised between the inner wall and the lateral surface of the 

 corallites is completely cellular. Large diagonal of the corallites at the upper surface of 

 the compound mass about 8 lines ; diameter of the true calice about 3 lines. 



Wenlock Edge. Aymestry, Herefordshire (M'Coy). 



Specimens are in the Collections of the Paris Museum, Bristol Museum, of the Museum 

 of Practical Geology, and M. de Verneuil. 



2. Strombodes Murchisoni. Tab. LXX, figs. 1, la, Id, \c, Id. 



Acervularia Baltica (pars), Lonsdale, in Murchison, Sil. Syst., p. 689, pi. xvi, figs. 8b, 



8c, 8d, 8e (Ccet. excl.), 1839. (Not Schwcigger.) 

 Actinocyathus Balticus, D'Orbigny, Prodr. de Paleont, vol. i, p. 48, 1850. 

 Strombodes Murchisoni, Milne Edwards and Jules Haime, Pol. Foss. des Terr. Palseoz. 



(Arch, du Mus., vol. v), p. 428, 1851. 



Corallum massive, subturbinate ; common basal plate covered with a very thick 



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