elaborating a most powerful inductive argument against the theory of evolution, and concluding that, so far from the history of these creatures favouring such a theory, it seems as if expressly contrived to exclude its possibility. But, while the gigantic Eurypterids and ornate Trilobites of the Devonian were rapidly approaching their end, a few despised little crustaceans,--represented by the _Amphipeltis_ of New Brunswick and _Kampecaris_ of Scotland,--were obscurely laying the foundation of a new line of beings, that of the Stomapods, destined to culminate in the Squillas and their allies, which, however different in structure, are practically the Eurypterids of the modern ocean. So change the dynasties of men and animals. "Thou takest away their breath, they die, They return to their dust; Thou sendest forth Thy Spirit, They are created; Thou renewest the form of the earth." The reign of fishes began in the Upper Silurian, for in the rocks of this age, more especially in England, several species have been found. They occur, however, only in the newer beds of this formation, and are not of large size, nor very abundant. It is to be observed that, in so far as the fragments discovered can be interpreted, they indicate the existence already of two distinct types of fishes, the Ganoids, or gar-fishes, protected with bony plates and scales, and the Placoids, or shark-like fishes; and that in the existing world these fishes are regarded as occupying a high place in their class. Further, these two groups of fishes are those which throughout a large portion of geological time continue to prevail to the exclusion of other types, the ordinary bony fishes having been introduced only in comparatively recent periods. With the Devonian, however, there comes a vast increase to the finny armies; and so characteristic are these that the Devonian has been called the age of fishes _par excellence_, and we must try, with the help of our illustration, to paint these old inhabitants of the waters as distinctly as we can. Among the most ancient and curious of these fishes are those singular forms covered with broad plates, of which the _Pteraspis_ of the Upper Silurian is the herald, and which are represented in the Lower Devonian by several distinct genera. Of these, one of the most curious is the _Cephalaspis_, or buckler-head, distinguished by its broad flat head, rounded in front and prolonged at the sides into two great spines, which project far beyond the sides of the comparatively slender body. This fish, it may be mentioned, is the type of a family highly characteristic of the Lower Devonian, as well as of the Upper Silurian, and all of which are provided with large plate-like cephalic coverings, sometimes with a long snout in front, and, in so far as is known, a comparatively weak body and tail. They were all probably ground-living creatures, feeding on worms and shell-fishes, and