XXVII, 



igio 



1 Chapman, Silurian Fossils of South Yarra, &c. 63 



A SYNOPSIS OF THE SILURIAN FOSSILS OF SOUTH 

 YARRA AND THE YARRA IMPROVEMENT WORKS. 



By Fredk. Chapman, A.L.S., &c.,- Palaeontologist to the 



National Museum, Melbourne. 

 {Read he/ore the Field Naturalists^ Oluh of Victoria, V6th June, 1910.) 



General Remarks. 



From about the year 1895 to the present time excavations have 

 been made along both sides of the Lower Yarra from Brander's 

 Ferry to some little distance beyond the South Yarra railway 

 bridge — roughly speaking, about a mile and a half in length — in 

 order to straighten and otherwise improve the course of the river. 

 This has been effected by cutting across two meanders. By this 

 undertaking the probability of floods in the low-lying parts of 

 Richmond and South Yarra has been prevented ; and at the same 

 time it has opened the water-way, thus giving better facilities for 

 boating, as witnessed in the institution of the Henley-on-Yarra 

 Regatta. The necessary excavations have been made chiefly 

 in the Melbourne bed-rock, of Silurian age ; but river silt, 

 marine and estuarine shell-beds, and basalt, all of Pleistocene age, 

 have also been met with in the work. The advantages which these 

 excavations have offered to palaeontology are incalculable, for the 

 mudstones and sandstones of South Yarra have been proved to 

 contain many forms of life not found elsewhere in Victoria. The 

 enormous heaps of Silurian mudstone, and the rarer impure sand- 

 stone, have been diligently searched, hammer in hand, by several 

 ardent fossil collectors, pre-eminent among them being our 

 fellow-member, Mr. F. P. Spry. He it is who deserves the thanks 

 of those who are helping to work out the Victorian Silurian fauna, 

 for having secured many a rare specimen which, but for a timely 

 examination of the excavated rock, would probably have been 

 covered up, or used elsewhere for filling in swamps and 

 depressions. 



To realize the value of some of the discoveries we need only 

 mention Pterygotus australis, a eurypterid or " sea scorpion," the 

 first found in Australia, which the late Sir F. M'Coy described as 

 near ^' Pterygotus bilobus, Salter, sp., of the black, flaggy, upper- 

 most Silurian rock of Lesmahago ; " the beautiful spinose brittle- 

 star Gregoriura spr'yi, the type of a new genus ; and the bivalve 

 Cardiola cormzcopice, Goldf, sp., which links our Silurian shallow- 

 marine deposits with those of Bohemia and Great Britain. That 

 these deposits were formed at the margins of the Silurian sea, and 

 were directly influenced by tides and currents, is proved by the 

 frequent occurrence of false-bedded shales and sandstones. This 

 is supported by the general aspect of the fauna, which consists 

 of organisms that lived in shallows and on mud flats, obtaining 

 their food, much as do their related forms at the present day, 

 from the decaying particles and small fry disseminated through 



