84 Proceedings of the Royal Society of Victoria. 



As compared with European species, and taking first P. 

 zorgense, Kaysei-,^ from Sprakelsback in the Lower Devonian 

 of the Harz, the corallites of our form appear to be larger, 

 the mural pores more numerous and the septal spines more 

 developed. Compared with P. sekannm, Siebel, as figured by 

 Kayser,- the corallites are again much larger, but the nature of 

 the septa differs radically and the pores are not so regular. 

 From the well-known P. prohleniatiaim., Goldfuss, it is also 

 separated by the difference of size of the corallites, the number 

 of mural pores and the septal condition. 



There is a very close connection between the genera Pleuro- 

 dictyu/n and Michelinia, and it is possible, as pointed out 

 by Professor H. Alleyne Nicholson, that these two genera 

 will eventually be united. At present corals of this type 

 occurring in Upper Silurian and Lower Devonian beds are 

 referred to P/eurodic/yiD/i, whilst corals of a somewhat similar 

 type occuring in higher Devonian and Carboniferous strata are 

 classed under Micheliiiia. A very full discussion of the relations 

 of these two genera will be found in Professor Nicholson's 

 works,'^ and also in a paper by Professor Julien Fraipont.* 



As regards the American forms it seems to approach nearest 

 to P. sfylophonn/i, Eaton,' from the Hamilton Group (Middle 

 Devonian). 



Taking all these facts into consideration, there seems to be 

 no alternative but to class these specimens as P/eiavdicfyiaii, 

 leaving the specific determination till more perfect specimens are 

 available. 



I have seen in the Upper Silurian (Wenlock) rocks of Yass, 

 New South Wales, a PleiirodictyuDi having every appearance of 

 the Victorian form, even as to preser\ation. Mr. John jNIitchell 

 has also recorded" the occurrence of Pletirodic/y7i/ii in the Bowning 

 Beds of the same district, associated with Calymefie Blumenhachii, 



1 Abliaiifl. Geol. Speeialkarte Preus. u. Tluu-iny. Staat., ISTS, ii., Heft 4, \\ '--9. t. 33, 

 f. 9, 10. 



2 hoc. cit, p. 227, t. 33, f. 8, 8a, ? 11. 



8 Tabulate Corals, pp. 141-143, 151, 152 ; Man. Pal., 1889, i., pp. 316-318. 



4 Sur les affinit^s des genres Favosites, Eninionsia, Pleurodictyum et Miehellnia a 

 I'occasion de la description d'une forme iiouvelle de Fa\ositide du calcaire carbonif^re 

 superieur. Ann. Soe. Geol. Beige, 18SS, xvi., p. 21-32, t. 1. 



5 Nicholson, loc. cit., p. 145, t. 22, c and d. 



6 Proc. Linn. Soc. New South Wales, 1887, ii. (2), p. 412. 



