Pcdd'ontology of Upper Silurian i?or//.s', Victoria. 83 



Genus— Pleurodictyum, Goklfuss, 1829. 

 (Petrefact. Germanipe, i., p. 113). 



Pleurodictyum, sp. (? P. megastomum, McCoy, M.S.) 



(PL III., Fig. 1). 



In the collection there are two specimens of casts of this coral 

 from Kilmore and several from the Mansfield district. They 

 occur solely as casts, and though there can be no doubt as to 

 the generic position, it would be difficult to assign specific 

 characters to them. The most perfect specimen" is from Kilmore, 

 and shows impressions of nine polygonal calices and a portion of 

 a tenth. These form a more or less circular corallum. Extending 

 across it there is an irregular depression, which may possibly 

 represent the impression caused by the vermiform body, and 

 would point to the fact that we have before us the basal 

 portion of the corallum, es^^ecially as the corallites are radiating 

 outwards. Tlie cell walls have been dissolved away, and their 

 position is shown by spaces traversed by bars representing the 

 infilled mural pores, so that we have only an internal cast 

 presented. The walls have been thick and the septa numerous 

 and represented by broken ridges, pointing to the fact that the 

 septa in the original condition were present as rows of spines 

 rather than as regular ridges. Tlie mural pores are large, 

 irregularly spaced and numerous, as represented by the bars 

 before mentioned. The tabular are slightly arched and not 

 perfectly smooth, but covered with numbers of small pits 

 representing in the original a slightly pustulose or spinous 

 appearance. The largest tabula has a width of ~ of an inch. 

 The specimen from Kilmore showing the ten corallites has a 

 diameter of i^ of an inch. 



From this short description it will be seen that there is very 

 little to go on as far as specific deliraination is concerned. Sir 

 Frederick McCoy has recorded^ a form as Pleurodictyuin megas- 

 iojiium from the Upper Silurian of the Upper Yarra District, 

 but so far as I am aware does not describe it. It is quite 

 possible that our form and this are one and the same. 



1 Ann. May-. Nat. Hi=t., 1S67, xx., p. 201. 



