THECID/E AND HELIOPORID.-E. 243 



litcs, Dana, Plasmopora, E. and H., Propora, E. and H., Pinaco- 

 pora, Nich. and Eth. jun., andLycllia, E. and H., the Cretaceous 

 Polytremacis, D'Orb., and the recent Hcliopora, De Blainv., of 

 which only the first five concern us here. Fishdipora, M'Coy, 

 which has often been included among the Heliolitidce, appears 

 to me, for reasons which will subsequently be given, to belong 

 rather to the Chcetctidce (or to the Moiiticuliporida;, if such a 

 family be ultimately established), and I shall consider it in 

 association with Constellaria and Monticulipora. The Palaeozoic 

 genera of the HclioporidcB are exclusively Silurian and De- 

 vonian, and there is such a close similarity in their general 

 structure that they require but comparatively brief notice. 



GeniLs Heliolites, Dana, 1846. 



(Wilkes's Expl. Exped. Zoopli., p. 541.) 



(PI. XIL, figs. 2-2 a.) 



Gen. Char. — Corallum spheroidal, pyriform, hemispherical, 

 or rarely ramose, composed of numerous closely contiguous 

 corallites, which are divisible into two distinct series. The 

 larger corallites are cylindrical, comparatively few in number, 

 and furnished with twelve lamellar infoldings of the wall, of 

 the nature of pseudo-septa, which fall short of the axis of the 

 visceral chamber. Small corallites completely investing the 

 larger ones, more or less regularly polygonal in form, provided 

 with distinct walls, which are completely amalgamated with one 

 another and with the walls of the larger tubes, and which are 

 not known to be provided with any apertures allowing lateral 

 communication. The small tubes have no septa, but have 

 numerous straight and complete tabula;, similar but somewhat 

 less numerous structures existing in the large tubes. No 

 columella. 



Obs. — The corallum in Heliolites is usually more or less 

 hemispherical or spheroidal in shape, the under surface covered 

 with a concentrically-striated epitheca, and having the calices 



