OCR Text |
Show 1876.] AND LITTORAL CORALS. 437 Breadth of calices -fe inch. Locality. Caribbean Sea. 1'his is allied to Oculina tenella, Pourtales.' SCLEROHELIA HIRTELLA, Pallas, sp. (Plate XLI. figs. 3, 4.) This fine species has been found at St. Helena, and as yet nowhere else; and no other form comprehended by the genus has been described. On a large Ostrea from the coast of St. Helena, there are several specimens which would at a glance be referred to the genus Sclerohelia ; and their examination, whilst it confirms this impression, proves the extraordinary amount of variation which the calices may present. The specific diagnosis is as follows:- The corallum has a thick stem and many branches, the coenen-chyma being very thick, glistening, and finely granular. The costal stride are slightly marked. The calices are alternate and opposite on the young branches and are placed irregularly on the larger ones, being generally but slightly prominent and shallow. The columella is well developed, being made up of 7 or 8 papillae. There are three complete cycles of septa ; and some of the fourth are found in one or two systems. The septa are very unequal and very projecting at the margin. The pali are well developed, and are placed before the secondary septa. Diameter of the calices -^ inch. A comparison between this structural description and that which can be given of the specimens on the Ostrea is very instructive. 1. A large dendroid mass having three large branches, two of which coalesce after some ramifications have been given off. Calice 1. This is on the thick branch ; and its base is costulate, and the surface granular. The shape is elliptical; the septa are in six systems ; and there are four perfect cycles in two systems, an incomplete fourth cycle in one, and three complete cycles in the others. The columella is composed of three oblong masses in a line ; the pali are thin, rather long, and are placed before two secondaries and two tertiaries on one half, and before two tertiaries and two secondaries in the other. In the next calice to no. 1 (2) the columellary masses have united and have assumed a dense structure, arched above. No. 3 is a calice on a small branch, the calice being rather more circular in outline; the columella has two side-papillse ; and two of the pali are wanting. And in another calice (4) the columella is as in no. 2; but the pali are thick and broad. On other branches of the same corallum there are some calices with four cycles of septa in four systems, and the fifth orders wanting only in the half of the other systems; and in some the columella is long and solid, or long and incomplete, or round and made up of many processes. On the surface of the trunk there are some calices which surmount rather elongated buds, and the septal number is not over 24, and the columella consists of one twist of a band-like structure greatly resembling a styloid columella at the top. |