It will lead us too far astray to follow in detail the history of the further discoveries of the ichthyosaurs during the early part of the nineteenth century. It may briefly be said, only, that no other group of extinct backboned animals excited more interest among scientific men. One incident will suffice. More than sixty years ago, an interesting deduction as to the living form of the ichthyosaurs was made by Sir Richard Owen. He observed that many of the known skeletons, as they were found in their rocky matrix, had a remarkable dislocation of the vertebrae at a certain place near the end of the tail, and, although such an appendage was quite unknown in other reptiles either living or extinct, concluded that the living animals had a terminal, horizontal, fleshy fin, very much like that of the whales and sirenians. Sure enough, discoveries made forty years later disclosed impressions in the rocks, not only of a large caudal fin, but also of a dorsal fin, as well as outlines of the flesh-covered paddles. The dislocation of the vertebrae at the place where the fleshy fin joined the more slender tail was due to the action of currents of water, or simple gravitation, upon a thin vertical fin and not, as Owen supposed, to the twisting of the terminal part as it fell to a horizontal position after partial decomposition of the soft parts. About twenty-five years ago, Professor E. Fraas, the present director of the Stuttgart Museum, described and figured very fully, not only specimens showing impressions of the fins and paddles, but also others of well-preserved and very complete skeletons of different species of ichthyosaurs from the Jurassic deposits of Würtemberg, in which remains of these animals occur in great profusion. His researches, and those of several authors since then, supplementing and confirming or disproving those of the many observers made during the preceding seventy years, have finally determined almost perfectly the complete structure of the more typical ichthyosaurs, enabling us to infer not a little as to their habits and distribution in the old Jurassic oceans. Within the past few years the discoveries of Professor J. C. Merriam of California have likewise added greatly to our knowledge of the earlier ichthyosaurs. It may now truthfully be said that of no group of extinct reptiles do we have a more complete and satisfactory knowledge than of the ichthyosaurs. [Illustration: FIG. 52.—_Ichthyosaurus quadricissus._ Photograph of specimen in Senckenberg museum, from Dr. Dreverman.]