FAMILIES AND GEITERA OE THE MADEEPORAEIA. 115 



D'Achiardi describes a single species from one specimen, whieli 

 lie considers the type of this genus, DiplocoBniastraea. He con- 

 siders that this genus, by having denticulate septa and a spongy 

 columella, differs from Biplocoenia. Unfortunately the internal 

 structures of M. d'Achiardi's specimen are not visible, notvfith- 

 standing the perfection of the superficial septa, costge, and colu- 

 mella. The form is described in ' Coralli Giurassici dell' Italia 

 Settentrionale,' Pisa 1881, p. 41. I introduce the genus into the 

 Alliance with a little doubt. 



G-enus Diplothecaste^a. 



Syn. Biplocoenia (non E. de Fromentel), Duncan, "West-Indian 

 Corals, Quart. Journ. Geol. Soc. vol. xxiv. (1867), p. 20, pi. i. 

 fig. 3. 



The colony is massive. Corallites tall, crovp^ded, polygonal, 

 united by a well-developed common wall which projects at the 

 calicular surface. Within the polygonal wall is a space occupied 

 by ccenenchyma of oblique vesicular dissepiments, and within 

 that an internal wall, whence arise the septa. This calicular wall 

 is circular in transverse outline, wavy and thin. Columella 

 lamellar, and often joined to one. of the septa. Septa wide apart, 

 unequal; cycles imperfect. Endotheca slight, within the inner 

 wall. Gremmation occurs from the coenenchymal space. 



Distribution. — Fossil. Miocene : West Indies. 



G-enus KoiLOOOEiiriA, Duncan. 



Sjn. Ph^llocoenia, Laube. 



Colony convex or subplane above, massive, low. Corallites 

 with an intermediate structure which is usually a second wall to 

 each, and which may fuse with those of others. Here and there 

 intermediate exotheca. Calices with well-developed costse, which 

 in section do not touch those of other calices. Septa well 

 developed, but short. Axial space large, hollow, and without 

 a columella. 



Distribution. — Fossil. Trias (St. Cassian) : Europe. 



This genus is founded to receive PJiylloccenia decipiens, Laube. 

 It is very well defined by the absence of columella, the short 

 septa, and the double wall, as seen in sections. Mr. Tomes 

 mistook the superficial view for Cyathocoenia, nobis, in a paper 

 read before the Geological Society of London and not yet pub- 

 lished. 



8* 



