IV. 



Some Extinct Sharks and Ganoid Fishes.' 



OUR conceptions of some of the more primitive groups of fishes 

 have been greatly modified during the past few years. The 

 discovery of nearly complete skeletons has shown that the frag- 

 mentary fossils originally compared with the corresponding hard parts 

 of existing animals truly belong to strange races of which no idea 

 could be formed from their examination alone. Sharks, sturgeons, 

 mud-fishes, and the fringe-finned ganoids, in Palaeozoic times seem 

 to have flourished under almost as many modifications as characterise 

 the modern bony fishes in the fauna of to-day ; and it becomes more 

 and more evident, as discoveries continue, that the common ancestors 

 of the class date back to a period hopelessly remote, so far as the 

 palaeontologist is concerned. 



Among those who have contributed an important share to the 

 formation of these new conceptions, Dr. Anton Fritsch, of Prague, 

 merits our special gratitude. He has for many years collected the 

 fossil vertebrata from the Permian gas-coal formation of Bohemia, 

 even preserving the pyritised specimens by removing the decayed 

 bone and taking electrotypes of the impressions; and his great work 

 descriptive of these fossils is the most painstaking and elaborately 

 illustrated monograph of its kind. Quite lately, a new instalment of 

 the third volume has appeared, and the account of the fishes is now 

 extended to include the Acanthodians and the first section of the 

 Palgeoniscids. 



Several years ago, in an earlier section of his work. Dr. Fritsch 

 published the first detailed description of the singular primitive 

 sharks known as the Ichthyotomi, supplementing the beautiful figures 

 and brief notes of M. Charles Brongniart in his monograph on similar 

 fossils from the French Coal-measures. Now, he adds further to 

 our knowledge of the sharks by a detailed chapter on the Acan- 

 thodians ; though in this case, unfortunately, he is able to contribute 

 comparatively few new facts of fundamental importance, merely 

 confirming, revising, and systematising the observations of previous 

 authors. 



1 Fauna der Gaskohle und der Kalksteine der Pkrm-formation Bohmens. 

 Vol. iii., pt. 2. By Professor Anton Fritsch Prague: F. Rivnac, 1893 



