As already mentioned, the _Oolithic_ formations show a great similarity of their fish-fauna to that of the Lias; but still more apparent is its approach to the existing fauna. Teeth have been found which cannot even generically be distinguished from _Notidanus_. The Rays are represented by genera like _Spathobatis_, _Belemnobatis_, _Thaumas_; the _Holocephali_ are more numerous than in the Lias (_Ischyodus_, _Ganodus_). The most common Ganoid genera are _Caturus_, _Pycnodus_, _Pholidophorus_, _Lepidotus_, _Leptolepis_, all of which had been more or less fully represented in the Lias. Also _Ceratodus_ is continued into it. * * * * * The _Cretaceous_ group offers clear evidence of the further advance towards the existing fauna. Teeth of Sharks of existing genera _Carcharias_ (_Corax_), _Scyllium_, _Notidanus_, and _Galeocerdo_, are common in some of the marine strata, whilst Hybodonts and Cestracionts are represented by a small number of species only; of the latter one new genus, _Ptychodus_, appears and disappears. A very characteristic Ganoid genus, _Macropoma_, comprises homocercal fishes with rounded ganoid scales sculptured externally and pierced by prominent mucous tubes. _Caturus_ becomes extinct. Teeth and scales of _Lepidotus_ (with _Sphærodus_ as subgenus), clearly a freshwater fish, are widely distributed in the Wealden, and finally disappear in the chalk; its body was covered with large rhomboidal ganoid scales. _Gyrodus_ and _Aspidorhynchus_ occur in the beds of Voirons, _Coelodus_ and _Amiopsis_ (allied to Amra), in those of Comen, in Istria. But the Palæichthyes are now in the minority; undoubted Teleosteans have appeared, for the first time, on the stage of life in numerous genera, many of which are identical with still existing fishes. The majority are Acanthopterygians, but Physostomes and Plectognaths are likewise well represented, most of them being marine. Of Acanthopterygian families the first to appear are the _Berycidæ_, represented by several very distinct genera: _Beryx_; _Pseudoberyx_ with abdominal ventral fins; _Berycopsis_ with cycloid scales; _Homonotus_, _Stenostoma_, _Sphenocephalus_, _Acanus_, _Hoplopteryx_, _Platycornus_ with granular scales; _Podocys_ with a dorsal extending to the neck; _Acrogaster_, _Macrolepis_, _Rhacolepis_ from the chalk of Brazil. The position of _Pycnosterynx_ is uncertain, it approaches certain Pharyngognaths. True _Percidæ_ are absent, whilst the _Carangidæ_, _Sphyrænidæ_, _Cataphracti_, _Gobiidæ_, _Cottidæ_, and _Sparidæ_ are represented by one or more genera. Somewhat less diversified are the Physostomes, which belong principally to the _Clupeidæ_ and _Dercetidæ_, most of the genera being extinct; Clupea is abundant in some localities. _Scopelidæ_ (_Hemisaurida_ and _Saurocephalus_) occur in the chalk of Comen in Istria, and of Mæstricht. Of all cretaceous deposits none surpass those of the Lebanon with regard to the number of