The following diagnosis of the species was published by MM. Milne-Edwards and Jules Haime in their last work, the ' Histoire Naturelle des Coralliaires,' vol. ii. p. 19 : —
" The corallum is elongate and subcylindrical, straight or slightly curved ; the lower two- thirds of the wall are smooth and glistening, but in the upper third there are small subequal and very slightly prominent costae. The calice is subcircular. The columella is fasciculate, and is composed of a small number of delicate ' tigelles.' There are four cycles of septa ; but in the halves of three systems the septa of the fourth and fifth orders are absent. The septa are thin, but externally they are slightly thickened. The pali are narrow and thick."
An examination of a series of forms referable to this species proves the general correctness of this diagnosis ; but still it is not sufficiently exact. Some rather important structural details, which were noticed by these careful naturalists in their 'Monograph of the British Fossil Corals' (Pal. Soc), are not contained in the above diagnosis, and yet they certainly should have been. For instance, the spreading base of the corallum narrowing rapidly into a more or less cylindrical stem, and the occasional perfection of the fourth cycle in all the six systems, are details which cannot be overlooked.
It is quite true that corals with broad bases may become detached above the base, and that they then possess a pedunculate appearance ; but the presence of a broad base is a positive structural peculiarity.
The occasional perfection of the fourth cycle has not been observed by me ; but it is consistent with the variability of the septal arrangement in other species in which irregular septal systems prevail.
The distinctive structural peculiarities of Caryophyllia cylindracea are the general shape, the condition of the wall, the development of the costae, and the septal arrangement.
Caryophyllioe with four cycles of septa complete in each of six systems, and with the incomplete arrangement noticed in the species under consideration, were formerly supposed to be extinct, and to have been restricted to the Cretaceous and Tertiary periods. The following are species with four perfect cycles : —
Caryophyllia Bowerbanki, Ed. & H., found in the Gault.
„ Bebeyana, Ed. & H., from the Chalk of Aix-la-Chapelle,
„ Bredai, Ed. & H., from the Maestricht Chalk.
„ cylindrica, Ed. & H.. from the Maestricht Chalk.
„ Haimei, Ed. & H., from the Maestricht Chalk.
„ Sismondai, Ed. & H., Turin Miocene, Sicily.
„ arcuata, Ed. & H., Older and Newer Pliocene.
Seguenza has, moreover, described many species with the four cycles fully developed from the Older Pliocene of Sicily.
A species with the same septal arrangement has been found in the volcanic sands of Guadaloupe.
2h2
