330 Albert V. James: 



Mr. F. Chapman lias not been able to determine the age 

 of these worms, but as there is field evidence that they are 

 of Ordovician age, they will be called tentatively in this 

 paper the " Ordovician worm beds." 



(c) On the right bank of Jackson's Creek, at the mouth of a 



small gully, 30 yards east of conglomerate Cj. Jlere 

 impressions of the gill jDlumes of the worm Trachyderma 

 * sp. occur in two very narrow bands. 



(d) The best imjDressions of Trachyderma were found on the 



right bank, about 300 yards down stream from the con- 

 glomerate C . At this spot Tracliyderma and Monograp- 

 tus were obtained on the same slal>. Many of the strata 

 here yield the tubes and gill plumes of tliis worm, which 

 Mr. F. Chapman has connected with the gill plumes 

 found at South Yarra in Lower Silurian rocks. (7). 



(e) On the right l)ank of Jackson's Creek, 30 yai'ds north- 



east of the dyke D.^ (Plate XXXII). llie writer found 

 three or four species <if Silurian graptolites. Graptnlites 

 from localities (d) and (e) were sent to Mr. F. Chapman. 

 They have not been named yet. but were pronounced to Ije 

 definitely Silurian. 



(f) At the point x (Plate XXXII.), fossils were found alxnit 



1862 (4), by members of the Geological Survey. Mr. F. 



Chapman has stated that tliese fossils are definitely 



Silurian. 

 Junction of tJit Upper Ordorician oii<] J.nuer -Silurian. — 

 Previous to 1918 the junction between the Silurian and the Ordo- 

 vician rocks had been placed one mile S.S.E. of the junction of 

 the creeks (6). As neither unconformity nor fossils had been 

 found, geologists were forced to rely on the study of dips and 

 strikes, and on this evidence alone the placing of the junction 

 there seems to have been justified, for there the dips become lower 

 and the direction of the strike is slightly altered. In this aiea it 

 is not safe to put too much reliance on v'ariation in strike and dip, 

 because these are much disturbed by faulting, pitehing and hill 

 creep. 



Two of the three editions of the geological quarter sheet No. 7 

 S.E., show the Ordovician rocks extending to the S.E. margin, 

 Avhile quarter-sht-et No. 2 S.W. shows Silurian extending to the 

 S.W. margin, thus making the edges of the sheets coincide with the 

 junction between the Ordovician and, Silurian sediments. A third 



