336 AM I OI DEI 



scales rhombic with slight peg and socket articulations ; but they may 

 become cycloid on the tail (Aetheolepis). 



Semionotids are found in Permian, Triassic, and Jurassic rocks. The 

 most specialised are the latest. Acentropliorus and Semionotus are still 

 fusiform. 



Acentropliorus, Traq. ; Permian, Europe and North America. Serro- 

 lepis, Quend. ; Saryodon, PI. ; Colobodus, Ag. ; Triassic, Europe. Semionotus, 

 Ag. ; Triassic, Europe, Soutli Africa, North America. Lepidotus, Ag. 

 (Fig. 316); Khaetic to Wealden, Europe; Jurassic, India; Cretaceous, 

 Brazil. Cleithrolepis, Eg. ; Triassic, N.S. Wales, South Africa. Aetheolepis, 

 A. S. W. ; Aplmelepis, A. S. W. ; Jurassic, N.S. Wales. Dapedius, Leach 

 (Figs. 313-15); Lias, Europe. Tctrayonolepis, Bronn ; Jurassic, Europe 

 and India. 



Family MACROSEMIIDAE. This family of Mesozoic fish is probably 

 allied to the Semionotidae and Eugnathidae. The body is elongate with 

 a usually much lengthened dorsal fin, which is divided in Propterus and 

 Notayoyus. The scales are rhombic, but may become very thin in the 

 later Jurassic forms (Macrosemius). They are provided with peg and 

 socket articulations. The fulcra also are somewhat degenerate, being 

 present on the caudal fin only in some (Macrosemius). Although delicate, 

 the skeleton is well ossified. The mouth is small, the hyomandibular 

 vertical or inclined forwards. The sides of the cranium are incomplete. 

 The opercular bones are complete, the branchiostegals numerous, and a 

 median gular has been found in Opliiopsis. A notochord of considerable 

 size persisted, since the centra are in the form of rings, which may be 

 double in the tail-region (Ophiopsis). Nine radials have been counted 

 at the base of the pectoral fin. The teeth are usually strong, pointed or 

 styliform, on the jaws and inner bones of the mouth [505, 512]. 



Legnonotus, Eg. ; Rhaetic, England. Ophiopsis, Ag. ; Histionotus, 

 Ag. ; Petalopteryx, Pidet, Macrosemius, Ag. ; Propterus, Ag. ; Notayoyus, 

 Ag. ; Jurassic, Europe. 



Family PHOLIDOPHORIDAE. Amioids of elongate shape. No coronoid 

 has been found in the lower jaw, but there may be a vestige of the splenial. 

 There are fulcra and more or less rhombic deeply overlapping scales, with 

 peg and socket articulations. The scales are of the lepidosteoid structure, 

 with fine canaliculi. The vertebral centra are often divided horizontally 

 into upper and lower elements (hypo- and pleurocentra), which, however, 

 never form double rings or crescentic wedges. It is chiefly on account of 

 the structure of the lower jaw that this and the next two families have 

 been removed from the Amioidei, by A. S. Woodward, and placed at the 

 base of the Teleostei. The allied Oligopleuridae bridge over the gap 

 between them and the next Order in some respects. 



The remarkable genus Thoracopterus, with huge pectoral fins and 

 a large and powerful ventral lobe of the caudal fin, was a ' flying fish ' 

 of the Triassic age. Giyantopterns, of similar form, is closely allied 

 (Abel [1]). 



Pholidophorus, Ag. ; Triassic and Jurassic, Europe ; Trias, Australia. 

 Thoracopterus, Bronn ; Giyantopterus, Abel ; Peltopleurus, Kner ; Trias, 

 Europe. Pleuropholis, Eg. ; Jurassic, Europe. 



