466 WILLIAM K. GREGORY 



Suborder 4. Ginglymodi Cope. 

 With opisthocoelus vertebrae. 

 Lepidosteidas, Lepidosteus , Up. Cretaceous to Recent. 



Suborder 5. Halecomorphi Cope. 

 (Amioidei Lutken.) 

 Trunk elongate; mouth large; predaceous, with piercing teeth. 

 Exhibiting a progressive advance in the direction of the Iso- 

 spondyli. 



1. Eugnathidas. Vertebras absent or incomplete. Examples: Eug- 

 nathus, Caturus, Trias to Cretaceous. 



2. Pachycormidas. Swordfish-like Amioids. Vertebral axis without 



segmental vertebras. Upper Lias (Lower Jurassic) to Upper 

 Cretaceous. 



3. Amiidae. Vertebrae complete. Pleuro- and hypocentra in caudal 

 region. Upper Jurassic to Recent. 



4. Oligopleuridas. Vertebras well ossified, with no distinct pleuro- and 



hypocentra. Scales very thin and cycloid. Upper Jurassic to 

 Upper Cretaceous. This family may deserve a higher taxonomic 

 rank (Dean). 



Cohort Teleostei 1 Owen. 



The difficulty of separating the lower Teleosts from the higher 

 Ganoids has been commented upon above (page 461). 



Although no phylogenetic series of genera has been definitely 

 traced, connecting the Lepidosteoidei (Holostei) and the Mala- 

 copteroidei, it is easy to arrange a morphological series 2 leading 

 back into some such Triassic Ganoids as the Pholidophoridse. 

 These show rhombic ganoid scales, small fin-fulcra, ring-like 

 centra, and no intermuscular bones (i. e. ganoidean characters), 

 combined with a carp-like form, homocercal tail, and no gular 

 plates. . The Leptolepididae furnish the desired transition to the 

 Isospondyli ; since they reduce the ganoine and fin fulcra, develop 

 a few intermuscular bones, and perfect the centra, changing the 

 rhombic into cycloid scales. In the early Cretaceous Clupeoids 

 the skeleton is so closely similar to that of the typical Jurassic 

 Leptolepididae that Smith Woodward 3 believes that the Clupeoids 

 "may well be direct descendants" of the Leptolepididae. 



1 reAeoS, perfect, oGziov, bone, 

 a See Plate XXX. 



2 Cat. Foss. Fishes, Brit. Mus., Part IV, 1901, p. vii. 



