Elements of geology, or, The Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments elementsofgeolog00lyel Year: 1868 532 FOSSIL FISH OF THE [Ch. XXVI. genera were afterwards published by Sir P. Egerton, whose labors in this field (including a synopsis of all the genera known in 1857) have been acknowledged by Professor Huxley as haying powerfully con- tributed to clear up his ideas when he undertook, in 1861, the difficult task of classifying these fishes. To the Russian zoologist, Pander, we are also indebted for a most able trea
Elements of geology, or, The Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments elementsofgeolog00lyel Year: 1868 532 FOSSIL FISH OF THE [Ch. XXVI. genera were afterwards published by Sir P. Egerton, whose labors in this field (including a synopsis of all the genera known in 1857) have been acknowledged by Professor Huxley as haying powerfully con- tributed to clear up his ideas when he undertook, in 1861, the difficult task of classifying these fishes. To the Russian zoologist, Pander, we are also indebted for a most able treatise on these ichthyolites. Pro- fessor Huxley's masterly essay is of a later date 'than Pander's, and contains a systematic arrangement of the British Devonian fish, which, he observes, are of surpassing interest, as comprising the oldest assem- blage of vertebrate animals of which we can be said to have any toler- ably complete knowledge; for no reptiles have yet been found older than those of the coal, and the Silurian fish are confined to a few isolated specimens, affording us a very scanty insight into the character of the piscine fauna anterior to the period of the Old Red Sandstone. The Devonian fish were referred by Agassiz to two of his great orders, namely, the Placoids and Ganoids. Of the first of these, which in the Recent period comprise the shark, the dog-fish, and the ray, no entire skeletons are preserved, but fin-spines called Ichthyodorulites, and teeth occur. On such remains the genera Onchus, Odontacanthus and Ctenodus, a supposed cestraciont, and some others, have been established. There are also some spiny fish of a family called Acan- thodidse, not yet well understood, and thought by Huxley to have some connection with the Placoids, although he admits that they may perhaps have still more claims to rank with the Ganoids, with which they have been usually classed. Among the Ganoids are the Cephalaspidas (see fig. 589, p. 526), rep- resented by several gene
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