(1) In the _Bibliotheca ichthyologica_ Artedi gives a very complete list of all preceding authors who had written on fishes, with a critical analysis of their works. (2) The _Philosophia ichthyologica_ is devoted to a description of the external and internal parts of fishes; Artedi fixes a precise terminology for all the various modifications of the organs, distinguishing between those characters which determine a genus and such as indicate a species or merely a variety; in fact he establishes the method and principles which subsequently have guided every systematic ichthyologist. (3) The _Genera piscium_ contains well-defined diagnoses of forty-five genera, for which he has fixed an unchangeable nomenclature. (4) In the _Species piscium_ descriptions of seventy-two species, examined by himself, are given--descriptions which even now are models of exactitude and method. (5) Finally, in the _Synonymia piscium_ references to all previous authors are arranged for every species, very much in the manner which is adopted in the systematic works of the present day. Linnaeus. Artedi has been justly called the father of ichthyology. So admirable was his treatment of the subject, that even Linnaeus could only modify and add to it. Indeed, so far as ichthyology is concerned, Linnaeus has scarcely done anything beyond applying binominal terms to the species properly described and classified by Artedi. His classification of the genera appears in the 12th edition of the _Systema_ thus:-- A. _Amphibia nantia._--_Spiraculis compositis._--Petromyzon, Raía, Squalus, Chimaera. _Spiraculis solitariis._--Lophius, Acipenser, Cyclopterus, Balistes, Ostracion, Tetrodon, Diodon, Centriscus, Syngnathus, Pegasus. B. _Pisces apodes._--Muraena, Gymnotus, Trichiurus, Anarrhichas, Ammodytes, Ophidium, Stromateus, Xiphias. C. _Pisces jugulares._--Callionymus, Uranoscopus, Trachinus, Gadus, Blennius. D. _Pisces thoracici._--Cepola, Echeneis, Coryphaena, Gobius, Cottus, Scorpaena, Zeus, Pleuronectes, Chaetodon, Sparus, Labrus, Sciaena, Perca, Gasterosteus, Scomber, Mullus, Trigla. E. _Pisces abdominales._--Cobitis, Amia, Silurus, Teuthis, Loricaria, Salmo, Fistularia, Esox, Elops, Argentina, Atherina, Mugil, Mormyrus, Exocoetus, Polynemus, Clupea, Cyprinus. Two contemporaries of Linnaeus, L. T. Gronow and J. T. Klein, attempted a systematic arrangement of fishes.