260 RECORDS OF THE AUSTRALIAN MUSEUM. 



Genus Desmidopora, Nicholson,' \^d)^. 

 (Geol. Mag., [3], iii., 1886, p. 289.) 



Desmidopora nicholsoni, sp. nov. 

 (PI. xl., fig. 2) 



Sp. Char. — Oorallum apparently forming irregular, lobate, or 

 sub-massive colonies of medium size, presenting on the weathered 

 surface a roughened or rasp-like appearance. Corallites long, 

 tube-like, approximately straight, but here and there gently 

 curved ; walls firmly united, slightly thickened, but not incrassated 

 nor the primordial walls visible. Calices either slightly oblique, 

 semilunar to transversely elongate, irregularly curved or poly- 

 gonal, occasionally sub-triangular and definitely circumscribed, ^or 

 as winding and to some extent sinuous grooves, when they often 

 become confluent ; shorter diameter one third of a millimetre, 

 longer diameter a half to one millimetre, but often reaching two 

 millimetres, and in some instances as much as five. Tabulae 

 numerous but distant, complete, horizontal or concave, seldom 

 oblique, on the same line in contiguous corallites or not. Mural 

 pores large and very irregularly distributed. Fission of tube 

 walls frequent, 



Obs. — Desmidopora nicholsoni is one of the most interesting 

 Palaeozoic corals it has been my good fortune to examine, and is 

 the means of introducing into Australian Palaeontology a very 

 unlooked for genus. 



The form of the corallura is not fully known, as all the speci- 

 mens so far observed are fragmentary. The external characters 

 do not appear to have been of a striking nature, but it is in a 

 transverse section that its very peculiar features become apparent. 

 The eye is at once struck with the diversity of form of the 

 corallites. Some are semilunar or sub-triangular, others poly- 

 gonal, with a longer diameter of half to one millimetre, and 

 definitely circumscribed. Interspersed with these are others of 

 an extraordinary irregularity of outline, becoming more or less 

 extensively confluent, entirely loosing their circumscribed outline, 

 and becoming winding and sinuous, looking like several normal 

 calices run into one ; externally such calices present a more or 

 less vermiculate appearance. These attain a longest diameter of 

 three millimetres, and in some instances of five millimetres. On 

 the other hand the shortest diameter in all the corallites is one- 

 third of a millimetre. Amongst the circumscribed corallites some 

 are triangular, with a long convex and two short concave sides ; 

 others with a convex long side, and two short straight sides of 

 about equal length, interspei'sed with almost truly quadrangular, 

 lenticular, and sublunar corallites, but always with one diameter 

 greatly exceeding the other. 



