Ordovician Rocks. 59 



(a) The Elphinstone Tunnel — Castlemaine Section. 

 This section for the first five miles is based mainly on the evi- 

 dence of the cuttings on the Melbourne-Echuca Railway from the 

 Elphinstone Tunnel (72 miles) to the 7T-mile post south of the 

 town of Castlemaine. The section for the next two miles is based 

 on observations made on the hills south and south-west of Castle- 

 maine. West of this in a direct line evidence is scanty. The grap- 

 tolites of the railway cuttings have been described by Dr. HalU. 

 With the record of his observations I kave rarely found it neces- 

 sary to disagree, but, thanks to greater facilities for travelling, the 

 opportunity has presented itself of filling in more detail. The rocks 

 at the western entrance to the tunnel dip Avest owing to inversion. 

 Tetragraptus fruticosus is to be found in a small drainage channel 

 south of the railway, indicating the Upper Bendigonian horizon. 

 The fine anticline mentioned by Dr. Hall^ is now obscured by sur- 

 face 'Soil, but calculating its position, I paced west, and was for- 

 tunate in locating the "repeat " outcrop of T. fruticosus near the 

 72-mile post. The calculation was afterwards found to have been 

 unnecessary as the anticline is cleaily shown on the side of the 

 road to the north of the line. The next observed graptolite beds 

 occur in the second cutting. Here two bands of fossilifarous slate 

 occur, and an anticline causes both to be repeated 3 while still an- 

 other band occurs further west. All are Wattle Gully {D. hifidus} 

 beds — Lower Castlemainian. 



The next outcrop, a few chains east of the 73-mile post (all mile 

 posts mentioned are those on the railway), has Phyllogroptvs typns 

 associated with the small form of Bidymograptus caduceus. D. hifi- 

 dus is not found. The horizon is Middle Castlemainian. Just past the 

 73-mile post the large form of B. codiicens occurs, and since it 

 again occurs along the line of strike less than half a mile to the 

 south and is there associated with Diplograptus sp. and Logano- 

 graptus logani, I have felt justified in indicating this as Upper 

 Castlemaine. Three chains further west of the mile post the samer 

 zone repeats, and about three hundred yards still further west Onco- 

 graptus upsilon may be found in light-coloured slates Avith a west- 

 erly dip, and a little further on Trigonograpfus. These beds are 

 best developed at the 73i-niile railway bridge. Here they are thick 

 almost horizontal beds of blue slate — probably the corrugated 

 trough of a geo-syncline. Fossils are common, but a very ta-ouble- 

 some cleavage — c-ommon in nearly horizontal beds — makes extrac- 



1 Geol. Castlemaine, op. cit. 



2 Geol. Castlemaine, p. 60. 



