OCR Text |
Show 1882.] CORALS FROM MADEIRA. 215 Both these specimens came from off the same shell. A smaller individual of this species presents the peculiar ornamentation of the costae near the calice and the shining epitheca. It is cylindrical in shape, and is just beginning to curve at the top ; and it is fixed, by a base with two small offshoots, within the hollow of the valve of a shell. The calice is widely open, but has sharp margins and very slender and somewhat exsert and tolerably bent primary and secondary septa. The primaries and secondaries are nearly equal; the tertiaries are much smaller; and the fourth and fifth orders of the fourth cycle of septa are very small. The larger septa are wavy within, very slender, and well separated. The columella occupies considerable space, and is composed of about eight twisted band-like lamellae, which are separate. The pali are very small, and closely resemble the trabeculae of the collumella ; but their union low down with the septa can sometimes be seen. They are before the second and third orders of septa. The corallum is excessively slender and transparent. Height of the coral T 5^ inch. At the base of the specimen just described, and within the same valve of a shell, is a very minute coral, which appears to be a still smaller form of Caryophyllia cyathus. It has a circular calice, six primary and six smaller or secondary septa; and there are twelve very small rudiments of the tertiary cycle. The larger septa are slightly enlarged at their inner ends; and there are no pali, the columellary trabecules being very small and apparently in one little bundle. It is evident from the study of these specimens that the peculiar shining costal covering which has been termed a pellicular epitheca, but which does not appear to be a true outer thecal covering, is always present. The thickness of the septa and their crowded state seen in the adults is a matter of growth; and it is clear that the first stage of the coral shows three cycles of septa, the tertiary being rudimentary, and that in a more advanced stage there are four perfect cycles. The full number of septa is obtained during adult age ; and the whole of the calcareous tissues increase then in thickness. In examining some pieces of worn coral, probably originally forming part of a large Dendrophyllia, I found a small Caryophyllia cyathus. It has the peculiar epitheca, and is just in advance of the smallest specimen just noticed, so far as its growth is concerned. There are four cycles of septa in some of the systems, and in the others only three. The columella is a twisted piece of tissue; and the pali are small but distinct and are before the secondaries. Hence the coral with three cycles of septa in its early stage has no pali; they appear before the secondaries a little later, and subsequently'before the tertiary ; and this takes place when the fourth and fifth orders of septa are complete in a system. Then pali are developed before a higher order and eighteen result. The pali are deep in the calice, but project upwards; and they send processes |