224 Miss M. M. Ogllvie — Microscopic and Systematic 



them only in the fact that the new groups of growth-lamellse 

 are always closely opposed to the foregoing. 



The " columellar " or " pseuclocolumellar " area of recent 

 Maclre])oraria is explained by the author as the morphological 

 equivalent of the " tabulate " area in most Palseozoic Madre- 

 poraria. The styliform or fasciculate " true " columella of 

 Tiirhinolia and its allies proves itself to be, structurally con- 

 sidered, a basal deposit, and is merely an upwardly arched or 

 entwined modification of the tabulge. The " pseudocolumella" 

 is, as already known, a mixed structure in which septal teeth 

 or outgrowths unite with irregularly distributed basal deposit. 

 It finds its antetype readily in the occasional warping of the 

 septal spines or inner ends loithin the tabulate area of certain 

 Palaeozoic genera. The " lamellar " columella is of especial 

 interest ; the author looks upon it as the remnant of a retro- 

 grade " main sejptum^'' affording therefore an important 

 phylogenetic link between so-called "tetrameral" and "radial" 

 symmetry of the septa wherever it occurs. 



Considerable differences are at present found in Madre- 

 porarian literature in the use of the terms "theca" and 

 " epitheca." The author accepts Heider and Ortmann's terms 

 '"'' ■pseudotheca'''' for a wall formed by lateral thickening of the 

 septa, and " eutheca^^'' or simply theca^ for a wall in which 

 independent centres of deposit are developed. Ortmann's 

 suborders of Madreporaria, Euthecalia, Pseudothecalia, Athe- 

 calia are, however, believed by the author to be based on an 

 erroneous principle, since all types with a porous wall are 

 placed among Athecalia. Porosity is looked upon by the 

 author as a secondary feature, the porous wall can be demon- 

 strated to be the morphological equivalent either of pseudo- 

 theca or of eutheca. A still more serious objection to these 

 suborders is the fact that not all Turbinolids possess an 

 eutheca ; neither do all Astraiids possess a pseudotheca as 

 Ortmann means, but cases occur in both those families where 

 the only peripheral support is afforded by the epitheca. The 

 author is inclined to think this was the primitive form of the 

 Madreporarian calyx, and to look upon both theca and 

 pseudotheca as later modifications associated with retrogres- 

 sion of the epitheca, greater prominence and rapid growth of 

 the septa, and very often with the processes of vegetative 

 budding. 



Certain coenenchymatous colonies, Madrepora, Turhinaria^ 

 &c., have been shown by the author to have thecal and septal 

 structure like the Turbinolids ; further absence of basal struc- 

 tures in the calyx other than columella. This throws a new- 

 light on the rchitionship of these types, and brings them along 



