INTRODUCTION. lxxi 



or costal radii of the neighbouring corallites, being confluent, and consequently the calices 

 not being definitely circumscribed. No exterior walls ; the interior mural investment 

 well characterised. The centre of the tabula presenting a columellarian tubercle. 



Typ. sp., Phillipsastrea Hennahi, D'Orbigny, loc. cit. ; Astrea Hennahi, Lonsdale, in Geol. Trans., 

 2d series, vol. v, tab. lviii, fig. 3. 



27. Genus Eridophyllum. 



Corallum composite, and increasing by lateral gemmation. Corallites tall, cylindroid, 

 and provided with a thick epitheca, which gives rise to a vertical series of short and thick 

 subradiciform productions that extend to the next individual and unite them together. 

 Tabula well developed, and occupying the central area circumscribed by the inner 

 wall. Septal apparatus occupying the annular area situated between the outer and inner 

 mural investment, but not extending into the inner or central area. 



Typ. sp., Eridophyllum seriate, nob. 



Third Tribe— LITHODENDRONIN^E. 



Axis of the visceral chamber of the corallites occupied by a stylilbrm or lamellar 

 columella. 



28. Genus Lithodendron. 



Phillips, Geol. of Yorkshire, vol. ii, p. 200, 1835 (but not Lithodendron of Schweigger, which is not an 

 admissible genus) ; Siphonodendron, M'Coy, in Ann. and Mag. of Nat. Hist., 2d series, vol. iii, 1849. 



Corallum composite, arborescent, or massive. Corallites cylindrical or prismatic- 

 Columella styliform, compact. Septa well developed, but not reaching to the columella. 

 Tabula well developed. Interior wall rudimentary. 



Typ. sp., Lithodendron irreyulare, Phillips, loc. cit., pi. ii, figs. 14, 15. 



29. Genus Nematophyllum. 



Nematophyllum and Stylaxis, M'Goy, loc. cit., 1849. 



Corallum composite, massive. Corallites prismatic, with a well- developed interior 

 wall. Columella lamellar. Septa well developed, and united by transverse dissepi- 

 ments, which extend to the columella, but do not constitute true tabulae. Exterior area 

 vesicular. 



Typ. sp., Nematophyllum arachnoideum, M'Coy, loc. cit., p. 16. 



