actum- 



sub-class v GAN0IDE1 75 



nally ornamented with striae, rugae, or . reticulations. The remote dorsal and 



anal fins opposed to each other ; the diphycercal caudal fin truncated at its 



hinder margin. Of the four series of imbricating keeled 



dermal scutes one extends along the back, another along the 



ventral border, and the other two smaller series along the 



Hanks. The ventral scutes form a ring round the region 



of the anus. Belonorhynchus occurs in the Trias of the Alps 



(Raibl, Perledo, Seefeld) and Australia (Hawkesbury Forma- saurichthys 



tion), and is represented by skulls and other fragments in »■"'"*■ . A -- To 



f* Mr ■> o iiat. S1Z6. Iuia*'Tic ' 



the Lias of England and Germany (Belonostomus acutus, Ag.). Kemnath.Wurt'em- 

 The teeth, jaws, and skulls from the Muschelkalk, Keuper, 

 and Rhaetic, described under the name of Saurichthys, Ag. (Fig. 134), probably 

 belong to Belonorhynchus. 



Order 3. HETEROCERCI. Zittel. 1 



Notochord persistent, but arches, spinous processes, and fin supports more or less 

 ossified; head covered ivith bony dermal plates. Opercular apparatus well developed, 

 and branchiostegal rays numerous. Infraclavicle present. Unpaired, and usually 

 also paired fins fringed with fulcra. Paired fins without scaly axis, but each pelvic 

 fin with a row of imperfectly ossified basal supports. A single dorsal and anal fin, 

 with articulated rays which are more numerous than their supports. Caudal fin 

 heterocercal. Scales rhombic or rhomboidal, rarely cycloidal. 



In their skeletal structure and the characters of their paired fins, the 

 Heterocerci agree so closely with the Chondrostei, that they are united with 

 the latter by Traquair under the ordinal name of Acipenseroidei. In their 

 outward aspect they bear a superficial resemblance to the Lepidostei. The 

 Chondrostei, Heterocerci, and Lepidostei, probably form three different 

 specialised branches from one and the same primitive group. 



Family 1. Palaeoniscidae. Vogt emend. Traquair. 



Trunk elongate-fusiform. Head bones more or less enamelled. Teeth slender, 

 conical or styliform. Scales ganoid, rhombic in shape, rarely cycloid on the trunk. 

 Devonian to Upper Jurassic. 



Gheirolepis, Ag. Jaws with an outer row of minute teeth and an inner row 

 of stouter teeth. Dorsal fin remote, arising behind the origin of the anal fin. 

 Scales very small, rhombic, or almost square. C. cummingiae, Ag. ; Lower Old 

 Red Sandstone, Scotland. C. canadensis, Whiteaves. Upper Devonian : Scau- 

 menac Bay, Canada. 



Canobius, Gonatodus, Traquair. Lower Carboniferous ; Scotland. G. moly- 

 neuxi, Traq. ; English Coal Measures. 



Amblypterus, Ag. Mouth and teeth small. Fins with delicate fulcra. 

 Scales smooth. Several species from Lower Permian (Rothliegendes) of 

 Rhenish Prussia, Bohemia, and France. A. latus, Ag. ; A. duvernoyi, Ag. sp. 



Eurylepis, Xewb. (Fig. 135). Small fishes with small fins, the fin rays not 



1 Traquair, 11. II.. The Ganoid Fishes of the British Carboniferous Formations Palaeont. Soc.) 

 No. 1, 1877, No. 2. 1901. — On Amblypterus, Palaeoniscus, Gyrolepis, ami Pygopterus (Quart. Journ. 

 Geol. Soc. vol. XXXIII. ), 1S77.— On Eskdale Fishes (Trans. Roy. Soc. Edinb. vol. XXX.), 1881. 



