CYSTIPHYLLOIDEA. 299 



phylloid corals, and is characterised by the fact that the endothecal 

 structures are more or less completely reduced to a vesicular tissue, 

 composed of lenticular cells, which are often of specially large size 

 in the centre of the visceral chamber, and in this region represent 



Fig. 180. — Structure of Cystiphyllum cylindricum, Lonsd., from the Wenlock Limestone of 

 Ironbridge. a, Transverse section, enlarged twice ; B, Part of a vertical section, similarly en- 

 larged. (Original.) 



tabulae (fig. 180). The septa are rudimentary, but are usually recog- 

 nisable as more or less distinct striae or ridges on the surface of the 

 calice. 



The type-genus of this family is Cystiphyllum itself, in which the 

 corallum is almost invariably simple (it is composite in the C. fruti- 

 cosum of the American Devonian rocks), and is usually conical in form 

 (fig. 181), though in some cases greatly flattened. The wall is well 

 developed, and the visceral chamber is entirely filled with a vesicular 

 tissue of obliquely disposed lenticular cells, which in the central region 

 of the corallum often show a well-marked arrangement in funnel-shaped 

 layers. The calice sometimes exhibits nothing but the rounded upper 

 surfaces of the lenticular vesicles just spoken of, but its surface com- 

 monly shows more or less marked radial ridges or radiating rows of 

 tubercles, which represent the septa. In some cases, as in the De- 

 vonian C. sulcatu7?i and C. lamellosum, a well-marked dorsal fossula is 

 present ; and in the latter species it is sometimes even possible to 

 recognise a disposition of the septal ridges in four groups, correspond- 

 ing with the four quadrants of a typical Rugose Coral. All the known 

 species of Cystiphyllum are found in the Silurian or Devonian rocks, 

 one of the commonest species being the C. vesiculosum (fig. 181) of the 

 Devonian rocks of North America and Europe. Through Actinocystis 

 a transition can without violence be effected between the genus Cysti- 

 phyllum on the one hand and Cyathophyllum on the other hand. 



Family 2. Calceolidce. — This family has been founded for a 

 number of remarkable Palaeozoic corals, of which the principal 

 genera are Goniophyllum, Rhizophyllum, Arceopoma, and Calceola. 

 The corallum in this family is simple and conical in form, very 



