GENERA OF FA VOSITIDyE. 



167 



tigated under the microscope, as it is to some extent masked in 

 the latter case by the broken and cribriform character of the 

 walls. The average diameter of the corallites is about two- 

 thirds or three-fourths of a line. The tubes are completely in 

 contact, and the walls of contiguous corallites are undistinguish- 

 ably amalgamated (fig. 24, a and b). Thin sections, whether 



Fig. 24. — A, Part of a transverse section of Artropora Australis, Nich. and Eth. jun., en- 

 larged eight times, showing the trabecular septa and porous walls ; B, Part of a vertical 

 section of the same similarly enlarged, showing the cribriform character of the walls, the 

 septa, and the rudimentary tabulae. Devonian (?), Queensland. (Daintree Collection). 

 In these figures the matrix, which is really transparent, is represented as if opaque. 



transverse or vertical, show that the walls of the tubes are 

 extensively porous and cribriform (fig. 24, a and b), being 

 pierced by numerous apertures, which place the visceral cham- 

 bers in direct communication. Transverse sections, further, 

 serve admirably to show the character of the irregular trabec- 

 ular septa, some of which are short and spiniform, while others 

 divide at their ends, or even unite with their neighbours. Ver- 

 tical sections show that the septa are upon the whole placed in 

 longitudinal rows, and they exhibit in addition occasional hori- 

 zontal trabeculae (fig. 24, b), which may be regarded as of the 

 nature of rudimentary tabulae. 



From a consideration of the above characters, it cannot be 

 doubted that we have to deal in Ai'ceopora with a genuine 



