82 A TASMANIAN SPECIES OF HALYSITES. 



' The collective evidence of these fossils is unmistakable. 

 They are all Silurian, and some of them, especially the 

 Raphistoma and one species of Murchisouia,are Lower Silurian 

 tvpes. 



' The lithological character and associations of the strata 

 east and west (that is, across the strike) of this formation 

 is the only evidence of their age, no fossils having yet been 

 discovered in any other of the group of formations comprised 

 ill the western country, except the Silurian mudstoues, etc., 

 of the Eldon Eiver. There can, however, be little doubt that 

 they are none of them later than Silurian, while some are 

 evidently referable to the very earliest epochs.' " 



To this extract Mr. Stephens adds the following note : — 

 " This is an extract from a Parliamentary Paper containing 

 Mr. Grould's Report on the geology of the country east of 

 Macquarie Harbour, including the limestones of the Gordon 

 River. The passage marked by single inverted commas 

 appears to have been read at a meeting of the Royal Society, 

 but is not printed among its papers." 



In Mr. Stephens' specimen, the fasciculo-reticulate corallum 

 measures two and a half wide by three inches long. The 

 intersecting reticulations, or fenestrules, as m the recently 

 described H. ausiralis, mihi,f are variable in size and shape, 

 but again, as in the latter, are round, oval, transversely 

 elongated, irregular, or polygonal (hexagonal and pentagonal), 

 varying in size from six millimetres by four, up to eleven by 

 eight millimetres, and even twenty-five by three, with inter- 

 mediate gradations, and a like variability in the angles of 

 junction of the various plates comprising the corallum. As 

 a rule, the rt-ticulations are longer in one direction than the 

 •other, but this does not always hold good. 



The coral is exposed on the weathered surface of a piece 

 of limestone, and only in a few places can the inner surf ices 

 of the plates be seen, whei*e they project above the surface of 

 the matrix, and are covered by Beekite rosettes. This altera- 

 tion and weathering have so far destroyed the finer points of 

 structure that it is not possible to ascertain the number of 

 corallites with accuracy in any one interstice, but sufficient 

 remains to indicate that they were numerous. In a few 

 instances the inter-corallite walls are still visible; these are 

 trenchant and narrow, leaving no-^room for the presence of 

 interstitial corallites, similar to those of the well-known 

 H. catemdatus, Linn. The whole of the corallites seem, 

 therefore, to be " normal," a.id indicate that we are dealing 

 with a species of the H. escharoides group, as distinguished 

 from those forms in which there are both normal and inter- 

 ;stitial corallite-s, typified by the species first mentioned. 



+ Rec. Austr. Mus. 1898, iii, No. 4, p. 78. 



