no Evolution and Distribution of Fishes 



Amazon, the Congo, or the Nile. Abundant deposits were 

 thus made annually in some places, continuously in others 

 where they would give rise to fine shales or lime precipitates, 

 to coarse cherts or sandstones where they were laid down 

 nearer the main river-beds, or to coarse conglomerates 

 where adjacent to the main river-channel. For the state- 

 ment made by Campbell (p. 935) when speaking of these 

 very rocks: "the coarse volcanic conglomerate, like those 

 of the Old Red Sandstone, is in all likelihood a torrential 

 flood gravel" is exactly duplicated by Baldwin Spencer, in 

 his description of the "Neoceratodus" region of Australia, 

 that is cited on p. 32 of this work. 



The bone-beds, varying in number from one to as many 

 as five in some areas, that so sharply appear amongst the 

 other strata, and which may be from a half-inch to as much 

 as nine inches in thickness, can be exactly explained as 

 sudden deposits of volcanic dust that, in a few hours or 

 days, had entombed and preserved myriads of plant and 

 animal remains. 



The biological assemblage of these Upper Silurian 

 deposits can now be considered. Except for the presence 

 of some species of Lingula in intercalated beds, or the oc- 

 casional intrusion of stunted forms amongst others to be 

 now named, the entire group of organisms is totally differ- 

 ent from that found in the typical marine strata of the 

 lower Silurian, the Ordovician, or the Cambrian. Myriads 

 of the phyllopod genus Ceratiocaris ; such genera of the 

 Eurypteridae as Pterygotiis and Eurypterus; entire ex- 

 amples or more or less broken fragments of the scorpioid 

 Palaeophonus ; a new genus of myriapod; tubercles plates 

 or entire examples of primitive fishes belonging to such 

 genera as Thelodiis, Lanarkia, Lasaniiis, Cyathaspis, Ceph- 

 alaspis, Auchenaspis and Tremataspis; abundant remains of 

 the problematic plant Parka decipiens; and not unfrequent 

 lycopodineous specimens; make up the whole. 



Now the writer hopes to show elsewhere that species of 

 Ceratiocaris like many other of the simpler Crustacea, are 

 and have been freshwater in habitat. The history of the 

 Eurypteridae evidently is that from some primitive pre- 

 cambrian freshwater ancestor of the Arachnida, one line 



