Lithostrotion Columnaria (_Wond._ p. 641, _fig._ 8).--Polyparium massive, solid, composed of aggregated, contiguous, parallel, prismatic tubes, each terminated by a star: cells shallow, multi-radiate, stelliform. Species of this extinct genus are common in the mountain limestone, in large masses, which, from the pentagonal form, and parallel arrangement of the tubes, appear like clusters of miniature basaltic columns.[242] [242] Lithostrotion striatum, Pict. Atlas, pl. xxxvii. figs. 5, 6. [Sidenote: CYATHOPHYLLUM.] Cyathophyllum. _Lign. 87, figs. 1, 2._ (_Wond._ p. 641, _figs._ 1, 3.)--Polyparium turbinated, simple or compound, internal structure transversely chambered or lamellated; cells polygonal, radiated, depressed in the centre. The corals of this genus are so abundant in the Silurian rocks, that the seas of that epoch must have swarmed with them. The simple turbinated forms are often several inches long, and being somewhat curved, have obtained the popular name of "_petrified rams-horns_." Upon slitting one of these corals vertically, as in _Lign. 87, fig. 1_, the axis of the polyparium, beneath the cell, is found to consist of thin transverse partitions, constituting a series of chambers. In the compound Cyathophylla, the germs of young cells, occupying the disc of a parent cell, are often met with. _Fig._ 3 represents a group of four germs on the parent cell, of _C. dianthus_, a common and beautiful coral of the Dudley limestone. [Illustration: Lign. 87, Corals from the Dudley Limestone. (_Sil. Syst._) Fig. 1.--Cyathophyllum turbinatum: an oblique longitudinal section, showing at a the transverse lamellæ, or cells, of the internal structure. 2.--The same species. 3.--Cyathophyllum dianthus: a Specimen, with four young germs arising from the disc below. 4.--The same species, with four adult cells. ] These corals are also prevalent in South Devonshire, and many of the elegant marbles of Babbicombe are figured by the sections of these polyparia.[243] [243] Cyathophyllum turbinatum, Pict. Atlas, pl. xxxvi. ------------- fungites, ibid. pl. xxxviii. Associated with the Cyathophylla in the Silurian rocks, are certain corals that attain considerable magnitude, and which are principally distinguishable by their internal structure. Such are _Cystiphyllum_, constructed of bladder-like cells, and _Strombodes_, composed of spirally contorted lamellæ, or plates (_Sil. Syst._ pl. 16^(bis), _fig._ 4). Other hemispherical masses, presenting on the surface concentric wrinkles, with very minute pores, are common at Dudley, and belong to the genus _Stromatopora_. [Illustration: Lign. 88. Fossil Corals. _Upper Silurian, Dudley._[244] Fig. 1.--Astrea ananas. 1_a_.--A polished slice of Marble, formed of Astrea pentagona. _Devonian. Torquay._ 2.--Syringopora ramulosa. _Mt. L. Derbyshire._