Sedimentary Rocks. 53 



(I.) Beds without Dicellograptus and Dicranograptus, 

 but containing Didymograptus, Diplograptus and 

 Climacograptus. The Ba 67 outcrop is typical. Simi- 

 lar beds occur on the Upper Djerriwarrh and else- 

 where. 



(II.) Beds with the same species as (I.), but with Didy- 

 mograptus rare, and containing Dicellograptus also. 

 These outcrop at Gisborne, along the Djerriwarrh 

 and Glendoon Creeks, and on the Toolern Creek. 



(III.) Beds differing from (II.) by the addition of 

 Dicranograptus, as at Ba 62, Ba 64, Dalrymple's and 

 other outcrops along Jackson's Creek, and also along 

 Evans Creek. 



The scattered nature of these -outcrops renders correlation diffi- 

 cult, but we are inclined, on phylogenetic grounds, to arrange 

 .the beds as under : — 

 Uppermost — 



(I.) Dicranograptus beds. 



(II.) Dicellograptus beds. 



(III.) Diplograptus-Didymograptus beds. 



Upper Ordovician records from other parts of the State, 24 and 

 from New South Wales, 25 seem to show the same three zones, 

 but throw no light on their stratigraphical relations. The absence 

 of Dicranograptidae from Ba 67, the common occurrence of Glos- 

 sograptus, Didymograptus and Cryptograptus, all forms found 

 also in the Lower Ordovician, and the diplograptid characters of 

 the commonest species of Climacograptus, are some of our rea- 

 sons for placing this outcrop below the others. On the Toolern 

 Creek a Dicellograptus is found, which is either D. Smithi, Rued., 

 or closely allied to it. Dicellograptus smithi is cited by Ruede- 

 mann 26 as indicating the tendency of a Dicellograptus to develop ■ 

 Dicranograptus characters. If this be so, Dicellograptus beds 

 would be expected below those containing Dicranograptus. In 

 America and Great Britain Diplograptus and Climacograptus 

 survive, as well as precede, the Dicranograptidae. They may 

 therefore occur in beds above the highest given in the above 

 table. From such beds Didymograptus would be absent. 



24. 13, p. 7 (Detailed references in footnote). 



25. 14. 



.26. 12, p. 109, et seq. 



