136 PEOF. p. MARTIN DUNOAN's EETISION OF THE 



septa are compact, and are united by tabulae and synapticula. 

 There is no intercalieular wall. 



Distribution. — Fossil. Trias: Europe. 



G-enus Mesomobpha, Pratz, Palceontogr. xxix. (1882), p. 118. 



Syn. Porites (pars). 



Colony massive, branching, gibbous, sometimes incrusting. 

 Calices small, shallow, not defined by ridges, but confluent with 

 septo-costre running in low curves over a flat surface. Septa 

 compact, with spinules on the sides and edge, indicating a tra- 

 beculate construction. Columella styliform. No true wall. 

 Synapticula stout, and when in the sclerenchyma between the 

 corallites giving a coenenchymatous appearance. Dissepiments 

 exist. 



Distrihution. — Fossil. Cretaceous : Europe. 



II. Alliance THAMNASTROIDA. 

 Colonial Plesiofungidaej varying in shape, massive, foliaceous, dendroid, 

 incrusting or not. Confluent septo-costa3 well developed, usually solid, 

 trabeculate. Calices superficial, widely open, large. 

 Genus Thamnastr^a, Lesauvage. 



Subgenus Centrastr^a, d'Orb. 

 Genus Clausastr^a, d'Orb. 

 Genus Pseudastr^a, Reuss. 

 Genus Pironastr^a, d'Achiardi. 

 Genus Reussastr^a, d'Achiardi. 

 Genus DiMORPHASXRiEA, d'Orb. 

 Genus Dimorphoccenia, E. de From. 

 Genus Stylom^andra, E. de From. ? 



Genus Thamnastejea , Lesauvage, Ann. des Sci. Nat. V ser. 

 t. xxvi. p. 328 (1832). 



The synonymy of this great genus has been correctly given by 

 Milne-Edwards and Jules Haime, ' Hist. Nat. des Corall.' vol. ii. 

 p. 555 (1857), and carried down by them to 1851. M. de Ero- 

 mentel's 'Introd. a I'etude des Polyp, foss.' (p. 211), published 

 1858-1860, is unfortunate in not bringing in the synonymy 

 published by Milne-Edwards and Jules Haime, and in not noticing 

 their able work. 



Lesauvage, Groldfuss, Blainville, d'Orbigny, Lamouroux, and 

 Def ranee diflered in their views regarding the genus ; and Milne- 

 Edwards and Jules Haime, criticizing the results of these natu- 

 ralists, and having an immense amount of original matter at hand, 



