During Triassic and Jurassic Periods 197 



First. It should be observed from his grouping of beds 

 on p. 145 that different combinations or sets of organisms 

 are found at different localities; also that there may be 

 several zones for medusae, several for the fish Leptolepis, 

 several for reptiles, etc. In other words there is often a 

 successional repetition. Second: the land forms were main- 

 ly dead when entombed, the marine ones were alive. 

 Third: all were quickly and perfectly covered over and 

 encased. And here we might note specially regarding the 

 remains of the various genera of Medusae. The writer 

 has often watched myriads of these cast up on many shores 

 from Scotland to New Jersey and Florida. If left exposed 

 to drying sun and wind even for three hours practically no 

 trace is left of their organization. Again the brittlestars 

 were killed and covered before they attempted auto-dis- 

 organization. As Walther himself well puts it also (p. 206) 

 "no putrifactive bacteria destroyed the muscle of the fish, 

 no scavengering crabs had devoured the dead corpse." 

 Fourth: the entombing substance was quickly and evenly 

 deposited; was an extremely fine crystalline dust or a 

 watery crystalline deposit; and it quickly hardened into an 

 extremely close uniform fissile rock. Fifth: some rapidly 

 destructive substance, agency, or set of phenomena caused 

 far-reaching death in the air( as for the pterodactyls and 

 insects), in freshwater (as for the leeches and ganoid 

 fishes), and later in the sea (as for the medusae, brittle- 

 stars, etc). Sixth. These fine deposits of crystalline lime 

 substance were at irregular intervals covered by thin de- 

 posits of darker and apparently aerial debris. Seventh. 

 As Walther accepts and explains, both kinds of deposits 

 were not solution-precipitates, they seem to be made up 

 of extremely comminuted crystalline or isolated particles. 



We would consider then that the entire Altmiihl-Solen- 

 hofen deposit represents a huge mass of coral rock-deposit 

 that was caught up by a volcano or volcanoes, ground up in 

 its vent during days, or even weeks of eruptions, crystalliz- 

 ed and then shot out over hundreds of miles of country. Vio- 

 lent winds, earthquakes, and poisonous gaseous discharges 

 meanwhile brought wholesale death to land or freshwater 

 animals; while the crystalline volcanic dust percolating 



