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61 corallum ; vestibules deep ; interstitial surfaces strongly angular. Acantho- pores small, very numerous, forming a more or less complete ring round each calice, and placed on tlie angular interstitial surface, superficially appearing as oblique rows, or encircling rings of small tubercles, or minute apertures. Moniliform annulations. or periodical thickenings of the walls confined to tlie peripheral region, wide, and generally confluent towards the final period of growth, and thus becoming comparatively individually indis tinct when separate, presenting an ohconate appearance in sections. Tabulae very sparingly developed, complete, but the calices sometimes closed by perforated diaphragms. Obs.—In the case of this species identification has chiefly depended on Lonsdale’s figure in Strzelecki’s work, hut the characters are so well marked that little difficulty has arisen in referring specimens to it. The figured example could not be found in the Department of Geology, British Museum, by the Writer. As in S. ovata, the corallum is dicliotomously branched, but, on the whole, S. tasmaniensis must be regarded as a less robust species than the form just named. The branches are sometimes enlarged and constricted in their course, and it not infrequently happens that the apices are hollow, from the apparent decay or disintegration of the corallites in the axial region. Lonsdale noticed 1 this peculiarity, and both he and Dana speak of specimens crushed completely flat, with the whole of the axial portion removed. The base of attachment has not hcen observed, at the same time the species attained some size, as Lonsdale mentions one four and a half inches in length. As distinguished from S. ovata and S. Leichhardti, the peripheral region in the species now under description is remarkably narrow, arising chiefly from the very gentle angle at which the tubes diverge from the imaginary axis, the strong angle of deflection visible in other species being quite absent. The corallites in the axial region are angular, but become cylindrical throughout their short peripheral course. The primordial wall is visible in the former, and throughout a considerable portion of the latter, as very little secondary organic thickening appears to have taken place until the peri phery of the corallum is approached. It is rare to meet with moniliform