Proceedings of the Scientific Meetings of the Zoological Society of London 1876

Page 519

432 PROF. P. M. DUNCAN ON DEEP-SEA [May 16, long and granular at the sides ; and there are not quite three cycles. The pali are broad and short, and look like continuations of the pri­mary and secondary septa. The columella is small and concave. Breadth of calice -^ inch. Height of corallum T ^ inch. Locality. Dredged up from Persian Gulf on Nulhpore. PARACYATHUS CORONATUS, sp.n. (PlateXXXVIII. figs. 11-13.) The base is broad, but not so wide as the calice ; and the whole is short, the costse being very distinct, prominent, unequal, and extend­ing to the base. The calice is elliptical in outline, and the larger septa are exsert and rounded. The calice is shallow ; and a circular ring of septa-like pali arises around the rather small columella. The septa are in incomplete four cycles ; and there are about 20 pro­longations into the inner circle. These pali are long and arched, the whole presenting the appearance of an intercalicular gemmation. Height of corallum T% inch. Breadth of calice Ay inch. Locality. On a shell in the Persian Gulf. There is often much difficulty in deciding whether one of the crowns of pali are really such, or only long spines attached to the septa on their inner margin near the central space. The importance of deciding the true character of the structures i3 great; for whilst the septal spine may be of specific importance, the presence of the pali as independent structures is generic ; for it in­volves the presence of other tissues-such, for instance, as an extra crown of soft tentacles. Every one who-has seen many of the small sessile corals usually called Astrangia, Phyllangia, and Ulangia amongst the Astrangiacese must have felt this difficulty. In some the spinose nature of the false palus is evident; but in other species an arbitrary custom appears to have decided that such and such are not septal structures but pali. In the Astrangiacese there must be evidences of endothecal struc­ture in the form of dissepiments, although Milne-Edwards says it is " peu abondante." Moreover the septa must have their free margins more or less incised, and not plain. The origin of the coral­lites from a basal expansion is part of the diagnosis ; but of course this fails with regard to the parent before basal expansions, or stolons have been cast, forth. If a corallite simply increases by basal expansions, or stolons, it is not necessarily one of the Astrangiacese ; for budding can take place in species of other groups so low down and close to the base that it appears to be, and may be, essentially basal. This is seen in a specimen of Ovulina cubaensis from the Caribbean, when Serpula have kept the branches from rising as usual. Moreover in the Sclerohelia from St. Helena there are some corallites close to the base, and continuous with it, which are not distinguishable from it. Corallites springing thus from a base more or less closely, and not having endotheca or serrate-edged septa, are not Astrangiacese ; so that without the necessity of determining what are and what are not pali, the difficulty in classification is somewhat removed.