308 Frederick (Jltcvpinan : 



tests varies from .05 to 1 mm. Numerous fine cracks and fissures 

 traverse the limestone in all directions, and are filled generally 

 with a black granular substance, which in this case may be a 

 basic mineral infilling, such as one of the sulphides. Otherwise 

 the limestone is fairly pvu-e, and no qxuvrtz grains were noticed 

 in the sections examined. 



The limestone found near Roan Horse Gully, which consists 

 largely of {I) Girrdnella pellets in a fine-grained matrix, and 

 also contains brachiopoda and joints of crinoids, is much paler 

 than the trilobite limestone, and generally of a light grey* colour. 

 (See PI. LX., Pig. 26.) This rock, also, has a nearly pure calcitic 

 composition ; and there is a marked absence of the black car- 

 bonaceous and other matter so abundant in the darker lime- 

 stone. No trilobite fragments were noticed in this rock, but 

 it appears, nevertheless, to be merely a different lithological 

 condition in the same geological stage. 



Systematic Description of the Fossils.' 



Plantae. 



Class Algae. 



Genus GirvaucJJa, Nicholson and Etheridge fil.. 1880. 



(P) Girvanella, sp. (PI. LX., Fig 23, PI. LXL, Fig. 26). 



Ohsfr)-(itio)is. — A hand specimen of grey limestone, rather 

 ])aler in colour than the trilobite rock, is composed largely of 

 ovoid pellets formed by an enwrapping or encrusting organism 

 like Girvanella. One of these pellets measures as much as 15 

 mm. in length. This rock was mentioned in a previous note 

 published in 1907."- when the limestone was ascribed to the 

 Silurian, partly on account of the prevalence of that form else- 

 where in Victoria in beds of similar age ; and also because of 

 the P/afi/strop/ua-like Orthid, accompanying it. The latter 

 fossils are here shown to- be distinct from Platystrophia 



1 .Mr. K. O. Thiele, B.Sc, K.G..S., who collected these specimens, has kindly presented 

 them to the National Museum, Melbourne. 



2 Vict. Nat., vol. xxiv., p. 34. 



