SUß-CLASS V 



GANOIDEI 



65 



plates bear six ridges radiatiiig outwards. The corresponding plates occurring 

 in the Trias, namely, in the bone beds of the Muschelkalk, Lettenkohle, and 

 Rhaetic, are distinguished by their larger size and a different niimber of ridges. 

 As a rule, the upper dental plates exhibit five, the lower ones only four 

 radiating ridges. The oldest known species {C. arenaceus^ Quenst.) was 



I 



Fig. 119. 



Ceratodus forsten, Krefft. Lateral aspect of fish (A), base of skull {£), and mandible (C). Recent ; Queens- 

 land. Br, Brancliial cavity ; c, Foremost rib ; d, Teeth ; na, Nasal openings ; PSpk, Parasphenoid ; Pt, Pterygo- 

 palatine ; Qu, Quadrate ; Vo, Voiiier (after Günther). D, Ceratodios kaupi, Ag. Mandibular tooth on bony base, 

 Vs nat. size. Lettenkohle ; Hoheneck, near Ludwigsburg. 



obtained from the Bunter Sandstone of Würternberg ; the latest, which are 

 the smallest, are discovered in Europe in the Bathonian of Stonesfield and 

 Northampton, England, in North America in the Upper Jurassic of Colorado. 

 Other examples occur in the Kota-Maleri beds of India, in the Karoo 

 Formation of South Africa, and in later deposits in Patagonia. A well- 

 preserved skull of C. sturi has been described by Teller from the Upper 

 Keuper of Polzberg, near Lunz, in Lower Austria. 



Sub-Class 5. GANOIDEI. Agassiz.^ Enamel-scaled Fishes. 



Trunk and tau usually covered with ganoid scales, rarehj naked or with hony 

 j^lates. Skull covered with dermal bones, or completely ossified ; pterygo-quadrate 

 arcade movably articulated with the cranium (hyostylic) ; gilt clefts feebly separated, 

 opening into a cavity covered with a hojiy operculum. Vertebral column cartilaginous, 

 or with various degrees of ossification. Fin rays articulated, and fulcra usually 



1 Cope, E. D., Trans. Amer. Phil. Soc. vol. XIV. 1871, p. 445 ; and Amer. Nat. vols. XIX., 

 XX., XXL, XXIII. (1885-89).— /^m-%, T. H., Preliminary Essay upon the Systematic Arrange- 

 ment of the Fishes of the Devonian Epoch (Meni. Geol. Surv. dec. X.), 1861. — Kner, B., Betrach 

 tungen über die Ganoiden als natürliche Ordnung (Sitzungsb. k. Akad. Wiss. Wien, math.-naturw. 

 Ci. vol. LIV.), 1866. — Liitken, Chr., Ueber die Begrenzung und Eintheilung der Ganoiden 

 (Palaeontogr. vol. XXII.), 1868. — Malier, Joh., Ueber den Bau und die 'Grenzen der Ganoiden 

 (Abhandl. k. Akad. Wiss. Berlin, 1834), l^Q.—Traquair, R. II., The Ganoid Fishes of the British 

 Carboniferous Formations. I. Palaeoniscidae (Palaeont. Soc), 1877, No. 2, 1901. — Vogt, C, Quelques 

 Observations qui servent ä la Classification des Ganoides (Ann. Sei. Nat., Zool. ser. 3, vol. IV.). 



VOL. II F 



