A treatise on zoology . thecal plates are more numerous near theirnuirgins. Certain species, in which the plates seem more rounded, notclosely apposed, and perhaps without canals, in which the anal pyramidhad four plates, and in which the hydropore was not tripartite {ix. had novalvular plates),have been separated by Haeckel (1896) as a genus, Awphora-cystis. Pirocydix, Barrande (1887), Ordovician,Bohemia (Fig. VIII.), had a pear-shaped theca trun-cate below for fixation (St), but still without truestem. The anal pyramid had six plates (As); other-wise it was much like Deutocytitis. The regula
A treatise on zoology . thecal plates are more numerous near theirnuirgins. Certain species, in which the plates seem more rounded, notclosely apposed, and perhaps without canals, in which the anal pyramidhad four plates, and in which the hydropore was not tripartite {ix. had novalvular plates),have been separated by Haeckel (1896) as a genus, Awphora-cystis. Pirocydix, Barrande (1887), Ordovician,Bohemia (Fig. VIII.), had a pear-shaped theca trun-cate below for fixation (St), but still without truestem. The anal pyramid had six plates (As); other-wise it was much like Deutocytitis. The regularityof the adoral plates in these two genera suggeststhat they may eventually prove to be early forms ofDiploporita or Rhombifera. The Lower Niagara rocks (Silurian) of Indianaand neighbouring states have yielded numerous formsresembling Aristocystis in external appearance andstructure of theca, but with an ambulacral systemapparently presenting three grades of have all been described under the generic. Fio. vm. Piroci/stis pirura, re-Tj- 7 , •, TT 7 ±- -1 stored outline on the name Hotocystites or Holocystis, a name previously evidence of Banandegiven to a coral, and therefore bound to yield to the V}: -?; Lettering as in . F)f. II. alternative Megacystis, Hall (1864-65). Some of theso-called species described by Hall and S. A. Miller seem to agree withAristocystis in the entire absence of arms and food-grooves, in the similarposition and structure of mouth (ambulacral orifice, S. A. M.), and anus( mouth, S. A. M.), w^hile a hydropore ( anus, S. A. M.) is often ob-servable, and occasionally a fourth opening (? gonopore) ; the positionsof the two latter are at varying distances between mouth and has described other species with similar structure, but with fouror five of the ^^ly-tes surrounding the mouth raised into elliptical fticets,apparently for the support of S23ines like those of Placocystis (p. 51);no groove connects these facets with the
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