CHORDATA. 157 



Order 4. Teleostei. Bony fishes with comb-like gills and (generally) 

 a hyoidean pseudobranch, with bony operculum and two valves in the 

 bulbus arteriosus. No optic chiasma, conus arteriosus, spiracles, or cloaca. 



A. Physoklisti. Swim-bladder, when present, without pneu- 

 matic duct. 



(a.) Lophobranchii. Exoskeleton of large dermal plates ; gills tufted. 

 Pegasus; Syngnathus acus, pipe-fish, and Hippocampus, sea-horse, 

 male with brood-pouch in which the eggs are hatched. 



J>.) Plectognathi. Compact forms with immovably fused premaxillae 

 maxillae ; vertebral column short (18-20 vertebrae) ; a swim-bladder. 

 Ostracion, box-fish ; Orthagoriscus mola, sun-fish. Diodon. 



(c.) Anacanthini, with soft fin-rays (Malacopteri) ; a swim-bladder. 

 Pleuronectidae, flat-fish. Gadus morrhua, cod, G. seglefinus, haddock, 

 G. merlangus, whiting. Fierasfer acus, parasitic in Holothuria. Ex- 

 ocoetus exiliens, flying-fish.. 



(d.) Pharyngognathi, some of the fin-rays spinous ; hypopharyngeal 

 bones fused ; a swim-bladder. Labrus, Scarus. Embiotoca, viviparous. 



(e.) Acanthopteri, with spinous fin-rays, and separate hypopharyngeal 

 bones ; mostly ctenoid scales. Perca fluviatilis, perch. Serranus 

 scriba, hermaphrodite. Gasterosteus aculeatus, stickleback ; the male 

 takes care of the young. Oottus. gobio, bull-head. Trigla, gurnard. 

 Gobius, gudgeon. Zoarces viviparus. Mugil. Anabas scandens, 

 climbing fish (Labyrinthici). 



B. Physostomi. Soft fin-rays and separate hypopharyngeal bones. 

 Swim-bladder, when present, with a pneumatic duct. Anguilla vul- 

 garis, eel ; the male does not enter rivers. Mursena, Gymnotus elec- 

 tricus. Clupea harengus, herring. Mormyrus with pseudelectric 

 organ. Esox lucius, pike. Salmo salar, salmon,, with a fatty fin. Cy- 

 prinus carpio, carp. Cobitis fossilis, loach, Siiurus, Malapterurus 

 electricus, sheat-fish. 



