50 Coelenterata. 



and Balanophylliids. The mode of shifting of the pali, in those Hexacoralla 

 which possess them, also affords proof that the calcareous septa bifurcate as 

 in the Tetracoralla. 



6erth( 1 ) traces the descendants of the Paleozoic Heliolitidae down to 

 the present day. The Heliolitidae are true Madreporaria and should be removed 

 from the Tabulata. The Tertiary and living Poeillopora and Stylophora are 

 the descendants of two species of Heliolites (interstinctus and parvistella) 

 which were already differentiated in Silurian times. Compared with other living 

 corals Poc. and StyJ. present many of the primitive characters of their Palaeozoic 

 ancestors; especially characteristic are the cosneuchyme, which is occasionally 

 tubular, and the strong development of simple transverse platforms (Boden) in 

 the calyx tubes. The Mesozoic Stylinidse (Gyathophora with small calicles) agree 

 in the structure of their skeleton with certain Palaeozoic Heliolitidae, some of 

 them can be traced without difficulty to Silurian species Plasmopora and 

 Propora - - in which septal costae have arisen. The Tertiary and living Astraeo- 

 porids (Gyphastraa, Siderastrcea, Heliastrcea) are obviously the perforate descen- 

 dants of Stylinidae with feebly developed septa. The Heteroccenia of Upper 

 Cretaceous times resembles very closely, in the structure of its coenenchyme, the 

 Proporidae in which the ccenenchyme has become quite vesicular, and the ele- 

 ments which traversed it vertically have been completely lost. Characteristic of 

 these Het. is a specially strongly developed septum which approximates them 

 to a large proportion of the living Madrepora with which the former agree 

 in the position and arrangement of the calicles and in the structure of the surface 

 of the coenenchyme. The Cretaceous differ from the living reef corals in that 

 their skeleton is imperforate. Probably the Madrepores which form tufted stocks 

 having, on the tip of the twig, lateral calicles set in a rosette around a larger 

 axial one, are derived from Het. in which a similar arrangement of calicles 

 had been already produced. The Coccoseridae (especially Protarcea), generally 

 included in the Heliolitidse, can be followed through the Mesozoic Astrocoenidae 

 to the Poritidae. Madrepora contains species the different phyletic origins of 

 which are masked by convergence. The group of M. Hemprickii is descended 

 from the Jurassic Stylohelia', the group of arabica is related to the Jurassic Dendro- 

 helia. - - The changes in the skeleton of the above named corals from the 

 Palaeozoic to the present time may be thus briefly summarised - - the knobby 

 and encrusting Palaeozoic species have grown out into branching forms, in corre- 

 lation with this there has been a dwindling of the epitheca, there have been 

 changes in the coenenchyme, the septa have become differentiated into cycles 

 of different size, in many species the skeleton has become perforate or porose, 

 a bilateral arrangement of the septa has arisen and there has been a gradual 

 complication of growth, of structure and of the skeleton and septal apparatus. 



Gerth( 2 ) describes a Heterastridium from Ceram and points out that the 

 occurrence of these Hydrozoa at Hallstadt (Eastern Alps), Kotel (Eastern Balkans), 

 the Karakorum Pass and at Ceram furnishes a further confirmation of the view 

 that there was an open-sea connection between these regions. The fossil de- 

 scribed by Tornquist (in 1901) from North Sumatra as Neostroma sumatrensis 

 is Actinacis sumatrensis. The author describes another A. from Transcaucasia. 



Grosch concludes that Lithostrotion and Petalaxis should be united. Pleuro- 

 cora and Turbinaria are near relatives of Lith.-Pet. Conaxis is closely allied 

 to Lomdaleia, their rudimentary vesicular coenenchyme shows their primitive 

 nature. The Trochosmiliaceae are the descendants of Glisiophyllum and Axo- 

 phyllum. Porosity is of no value as a systematic character. The aporous 

 species of Lith.-Pet. of Carboniferous times gave rise to the perforate Pleur. 



