464 WILLIAM K. GREGORY 



nopteroti among Crossopterygians) ; the large conical teeth are 

 separated by intervening minute teeth (cf. Rhizodontidae among 

 Crossopterygii but also Cheirolepis among Heterocerci) ; the 

 opercular series is incomplete ; the paired fins apparently exhibit 

 a very feeble lobation (A. S. Woodward) ; fin fulcra are minute or 

 absent; the sclerotic ring was probably ossified (cf. Undina 

 among Crossopterygians) . 



Superorder Lepidosteoidei Bridge. 



(holostei J. Muller in part.) 



(Plate XXIX.) 



The superorder includes those Actinopterous Ganoids which are 

 Lepidosteoid in the larger sense ; it may have been derived from 

 some such forms as the Catopteridse (page 463) among the 

 Acipenseroidei, and indeed its oldest and most generalized 

 representative, Acentrophorus of the Upper Permian, was long 

 mistakenly referred to the Palaeoniscidae. But the group has 

 progressed beyond the Chondrostei in the following assemblage 

 of characters: 



Notochord and vertebras varying inversely in development, 

 the vertebrae ranging from incomplete pleuro- and hypocentral 

 rings to complete centra. Teeth well developed. Chondrocra- 

 nium more or less completely replaced by cartilage bones 

 corresponding to those generally present in Teleosts, "while 

 the palato-pterygoid cartilages, likewise modified by the growth 

 of cartilage bones, separately articulate with the lateral ethmoid 

 regions instead of meeting in a ventral symphysis beneath the 

 basis cranii " (Bridge). A supramaxillary (derived from the 

 hinder portion of the maxillary) . The preoperculum no longer 

 extending over the cheek but coming into intimate relation with 

 the pterygoquadrate series and assisting in the support of the 

 mandible (see p. 462). Opercular apparatus usually complete, 

 with branchiostegal rays and often a gular plate ; a bony supraoc- 

 cipital in the higher types ; baseosts in paired fins reduced, in pelvic 

 fins lacking. The dermal rays in all fins extensively developed, 

 equal in number to the endoskeletal supports. Infraclavicles 

 replaced by cleithra (clavicles) meeting in a ventral symphysis. 

 Fulcra on median and paired fins present, or reduced in later 



