The external aspect of these fossils is that of a cluster of cylindrical pipes, more or less parallel, connected by short transverse branches. They are the Tubiporites of Mr. Parkinson, who has given admirable figures of several specimens.[241] In these fossil corals that excellent observer first detected the animal membrane. A slab of marble, whose markings are produced by the section of the inclosed tubes of a Syringopora, is represented, Wond. p. 644, fig. 2. The Mountain limestones of Derbyshire, and of Clifton, on the banks of the Avon, contain figured marbles of this kind, which are manufactured into vases, tables, &c. The genus is extinct.
[241] Pict. Atlas, pl. xxxv. fig. 1. Syringopora geniculata, Pict. Atlas, pl. xxxiv.
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.
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.