Families of Tdeostean Fishes. 163 



Group 5 to Suborder VII. (part.) ; and Group G to Sub- 

 order XIII. 



Fuller definitions of the families, with an indication of the 

 principal genera contained in each, will be given in the forth- 

 coming seventh volume of the ' Cambridge Natural History.' 



Suborder I. Malacopterygii. 



Air-bladder, if present, communicating with the digestive 

 tract by a duct. Opercle well developed. Pectoral arch 

 suspended from the skull ; mesocoracoid arch present. Fins 

 without spines, the ventrals abdominal, if present. Anterior 

 vertebra? distinct, without Weberian ossicles. 



This suborder, which corresponds to the Isospondyli and 

 Scyphophori of Cope and to a part of the Isospondyli of 

 A. S. Woodward, embraces the most generalized of the 

 Teleosts, and is intimately connected with the Holostean 

 Ganoids by the fossil forms which are placed at the base of 

 the series of families. The physostomous condition of the 

 air-bladder, the connexion of the pectoral arch with the skull, 

 the presence of a mesocoracoid arch, the backward position of 

 the many-rayed ventral fins, the normal condition of the ante- 

 rior vertebra?, the absence of true spines to the fins, and the 

 separation of the supraoccipital bone from the frontals by the 

 parietals are primitive characters which occur combined in 

 some families of this suborder only. The mesocoracoid arch 

 is retained by the Ostariophysi, which differ in the remarkably 

 modified condition of the anterior vertebra?, but it disappears 

 in all other Teleosts, which gradually acquire a more forward 

 position of the ventral fins and a reduction in the number of 

 their rays, develop spines in the vertical fins, and lose the 

 communication of the air-bladder with the outside. 



The Malacopterygii may be divided into twenty-one 

 families : — 



I. Fins fringed -with fulcra, or scales coated with ganoine ; notochord 

 usually continuous through the vertebra (connecting forms 

 between Ganoids and Teleosts). 

 Vertebral centra not more than rings ; fins with 

 fulcra ; scales rhombic, united by peg-and- 



socket 1. Pholidophoridce f. 



Vertebral centra not more than rings ; fins with 



fulcra ; scales cycloid , 2. Arch<so»uenid(S t. 



Vertebral centra complete or with minute per- 

 foration ; fins with fulcra ; scales cycloid . . 3. Oligopleuridce f. 

 Vertebral centra nearly complete, but with per- 

 foration ; no fulcra ; scales cycloid 4. Leptolepididce f . 



f This sign indicates that the family is represented bv fossil forms onlv. 



11* 



