68 W. J. Harris; 



the Darriwil beds. Dr. HalU states that in the Bendigo beds " D. 

 caduceiis is rare and small, and it is interesting to notice as wq 

 pass up through a long succession of rocks above these of Bendigo 

 that it increases in relative numbers and at the same time attains 

 a much larger size till it reaches its maximum near the horizon of 

 the uppermost Castlemaine beds, where it crowds the rocks to almost 

 entire exclusion of other forms. It then enters on the period of 

 its decline, and is but sparingly represented by stunted forms at 

 Darriwil, and perhaps ranges into the Upper Ordovician." Later 

 Dr. Hall2 expresses his doubt as to the occurrence of D. caduceus 

 with T. fruticosvs, and I have not found them together. With D. 

 bifidu-s, D. caduceus is rare and small. In the Middle Castleinaine 

 beds it is fairly common but small. In the Victoria Gully beds it- 

 is very numerous, and the specimens are larger than those of the 

 lower loeds. Here the rhabdosome is of horse-shoe shape, the stipes 

 are of even width throughout, and a long nema is often present. 

 In the McKenzie's Hill beds D. caduceus is even more common than 

 in the Victoria Gully beds, where Dr. Hall-^ estimated it to comprise 

 So per cent, of the fauna. In typical specimens from this upper 

 zone the stipes diverge at the angle of about 330^, and the branches 

 widen as they diverge and then narrow somewhat towards their dis- 

 tal extremities. The rhabdosome is now more like the letter V than 

 U. In the beds west of McKenzie's Hill B. caduceus varies greatly, 

 though it seems as if the maximum of variation is in the McKenzie's 

 Hill teds. The stipes are longer than ever, but not so wide. Stipes 

 measuring over 60 mm. in length are not at all uncommon. The 

 forms of the two zones contrast in the same way as the tall thin- 

 branched trees of a forest do with the sturdy, wide-spreading trees 

 of the more open country. The contrast is not so great between 

 the higher beds of the McKenzie Hill zone and the lowest Oncograp- 

 tus beds. Measurements of twelve specimens on one slalj from an 

 outcrop near the Muckleford Railway Station, showed an angle of 

 divergence varying from 315° to 335°, the average being 

 325°. Several of the specimens have stipes more than 60 

 mm. in length. D. caduceus, Salter var., inanuhriattis, 

 T. S. Hall, and D. forci piformis. Rued., botli late deriva- 

 tives of D. caduceus, are somewhat rare in the McKenzie's 

 Hill beds, and more abundant in the western beds, being more com- 

 mon at some outcrops than at others. As Dr. HalH noted, the thecal 



1 Grap. Rocks of Vict., p. 443. 



2 Recent Advances of our Knowledjfe of Victorian Graptolites. A.A..4..S. (1900), p. 310. 



3 Geol. Castleniaitie, p. 71. 



4 Victorian Graptolites, Part IV. Proc. Roy. Soc. Victoria, xxvii. (n.s.), part i., 1914, p. 109. 



