1 86 Evolution and Distribution of Fishes 



where delicate plants could be preserved in the fine muds, 

 were killed by the sudden silting up of the lake or estuary 

 with beds of coarse sand or gravel, swept down by powerful 

 floods of freshwater." 



But Woodward in his later memoir {141: 10(1908) 

 when speaking of collections from the same formation, but 

 at St. Peters locality says: "The fish-remains obtained by 

 Mr. Dunstan from the Hawkesbury formation at St. Peters 

 belong to two distinct series, which are described separately 

 in the following memoir. The first and much the largest 

 series was discovered in a dark indurated shale, which splits 

 with a more or less irregular fracture; while the second 

 series was found in a grey mudstone closely resembling that 

 in which numerous fishes occur at Gosford. The skeletal 

 parts of the fishes in the first series are actually preserved, 

 though considerably stained and partly obscured by the 

 oxide of iron and manganese, with some pyrites." 



"The fishes of the second series occur chiefly as im- 

 pressions on the rock, which are stained black zvith a thin 

 film of bituminous material, resulting from the decomposi- 

 tion of the original organic tissues. In both cases the fishes 

 appear to have been complete when buried, and show no 

 signs of having been disturbed by currents or by predaceous 

 animals. Like most well-preserved fossil fishes, they prob- 

 ably denote some local accident, which suddenly destroyed 

 and entombed them." 



The writer would again suggest here that as such fish 

 would become putrid, softened, and disintegrated within 

 a week in freshwater, and as the fine mudstones indicate 

 no violent mode of detrital deposit in relation to the organ- 

 isms, death by volcanic shock or gaseous discharge took 

 place, with immediately succeeding entombment amid vol- 

 canic dust, either under water, or in shallow water that in 

 a day or two became dried up and sun-exposed. The whole 

 then probably firmed, and gradual exudation of oily 

 material sealed the organisms, as well as furnished the 

 chemical basis for transformation of their oils into bitumin- 

 ous products. Woodward has the following list from the 

 Gosford beds : 



