FAMILIES AND GEISEEA OF THE MADREPOBAEIA. 169 



development. Calices circular on dome-like projections, with a 

 central, circular, well-marked fossette. The septa are nume- 

 rous, toothed, uniting and joined by well- developed synapticula. 

 The basal epitheca well developed, and biding delicate and nume- 

 rous costse. 



Distribution. — Fossil. Cretaceous : Europe. 



Grenus Thamnar^a, Etallon, Lethcea Bruntrutana, p. 411 (1864). 



Colony branched or elongate, dense, strongly perforate as if 

 vermiculate. Calices superficial. Columella sometimes tuber- 

 cular. Septa confluent, irregular, more or less bent and echinu- 

 late (perforate in the delineation). Wall absent. Synapticula ? 



Distrihution. — Fossil, Jurassic : Europe. 



This genus, with a very Microsolenian facies, is allied to the 

 Perforate genus Psammocora by Etallon. E. Pratz places it, 

 however, in the neighbourhood oi Microsolena. 



Genus Dipiar^a, MilascJiewitscli, NattTieim. Korallen, Abth. ii., 

 PalcEontographica, xxi. p. 2^9 (1875). 



Colony dendroid, with a broad basal stem ; branchlets more or 

 less vertical. Calices more or less oval in outline, rounded off" at 

 the margin, and shallow. Columella spongy. Septa numerous, 

 anastomosing, thick at the wall, thin near the centre of the calice ; 

 they are perforate near their inner ends. Synapticula well 

 developed. 



Distrihution. — Fossil. Jurassic : Europe. 



The illustration shows costse, and probably there was an 

 epitheca. 



Genus Disar^a, de Fromentel, Introd. Polyp, foss. p. 245 

 (1858-1861). 



The colony is branched and in low bush-shaped forms, and the 

 corallites arise low in the primary stem, and grow upwards, not 

 separating much. There is no wall to the corallites, and the 

 ealicinal parts are convex and rounded, the calices having a cir- 

 cular fossette in their axis. The septa are very numerous and 

 delicate, being composed of nodules and processes, the first being 

 joined to the corresponding structures of the neighbouring septa. 

 The costse are covered with a delicate epitheca. 



The author of this genus states that the internal construction 



