SUB-CLASS V 



GANOIDEI 



65 



plates bear six ridges radiating outwards. The corresponding plates occurring 

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

 Khaetic, are distinguished by their larger size and a different number 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 



Fig. 119. 



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

 land. Br, Branchial cavity ; c. Foremost rib ; d. Teeth ; na, Nasal openings ; P,S'j)/i, Parasphenoid ; Pt, Pterygo- 

 palatine ; Qj(, Quadrate : Vo, Vomer (after Gtinther). D, Ceratodus Imupi, Ag. Mandibular tooth on bony base, 

 Vs uat. size. Lettenlsolde ; Hohenecl-;, near Ludwigsburg. 



obtained from the Bunter Sandstone of Wiirtemberg ; 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. 



Trunh and tail usually covered with ganoid scales, rarely naked or ivith bony 

 plates. Skull covered with dermal hones, or comjMely ossified; pterygo-qaadrafe 

 arcade movahly articulated with the cranium (hyostylic) ; gill clefts feebly separated, 

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

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



^ CojK, E. I)., Trans. A.mer. Phil. Soc. vol. XIV. 1871, p. 445; and Amer. Nat. vols. XIX., 

 XX., XXI., XXIII. (1885-89).— /r?/a;Zey, T. H., Preliminary Essay upon the Systematic Arrange- 

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

 tungen liber die Gauoiden als natiirliche Ordnuiig (Sitzungsb. k. Akad. Wiss. Wieu, math.-uatiirw. 

 01. vol. LIV.), 1866. — Liitken, Chr., Ueber die Begrenzuug und Eintheihmg der Gauoiden 

 (Palaeontogr. vol. XXII.), 1868. — Mllller, Joh., Ueber den Ban und die Grenzen der Ganoideu 

 (Aljhandl. k. Akad. Wiss. Berlin, 1834), l^-m. — Traquair, R. H.. The Ganoid Fishes of the British 

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

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



VOL. II F 



