54 Harris and Crawford: 



(b) Relation to Lower Ordovician — Critical Sections. 



As far as the writers are aware, there is no record of the ob- 

 servation of the junction of Upper and Lower Ordovician in 

 Victoria. Between Ba 67 and Ba 70, the nearest outcrops of 

 Upper and Lower graptolite shales shown on the Quartersheets, 

 the distance is 7\ miles. Our discovery of Upper Ordovician. 

 fossils at Gisborne narrowed the gap to less than two miles. By- 

 making traverses further south we still further reduced this dis- 

 tance, and finally succeeded in ascertaining the junction within a 

 few yards. The actual junction cannot be indicated, since, unless 

 one were to judge by lithological characters, there is no evidence 

 by which Upper and Lower Ordovician unfossiliferous rocks 

 may be distinguished. Taken as a whole, Lower Ordovician 

 sandstones are unlike those of Upper Ordovician age, but the test 

 is not one which can be safely applied to any limited outcrop. 

 The shales are more distinctive, but cannot invariably be recog- 

 nised by texture and colour. 



An account will now be given of some sections across the 

 boundary line, commencing near the north of the area, and work- 

 ing south. 



(I.) From the extreme north of the district, Messrs. Skeats 

 and Summers 27 record graptolites obtained near " Cheniston,"" 

 Upper Macedon. Dr. Hall referred these to the Darriwil -series. 

 In the same beds we discovered Loganograptus logani, confirm- 

 ing the reference to Lower Ordovician. To the east of the Bar- 

 ringo Creek badly preserved graptolites were found in meta- 

 morphosed shales. "Whether they were Upper or 27a Lower Ordo- 

 vician could not be determined. North of Riddell's Creek, fur- 

 ther east, Diplograptus and Climacograptus were obtained. 



(II.) North of Gisborne township, a short distance upstream, 

 from Cherry's saw mills, Lower Ordovician graptolites occur. 

 Arenaceous shales in the bed of an old channel of Jackson's 

 Creek yielded — 



Didymograptus caduceus, Salter. 



Didymograptus, spp. 



Tetragraptus quadribrachiatus ; J. Hall. 



Diplograptus, sp. 



Glossograptus, sp. 



Loganograptus, cf. logani. 



27. 4, p. 41. 



27a. The discovery of Climacor/raptns bicorn/iti, var. peltifer, Lapw. var., has since shown 

 these beds to be Upper Ordovician. 



