574 



CHORD AT A. 



cycloid scales. The living forms (the group appears in the trias) have ossi- 

 fied opisthocoelous vertebrae and diphy- or homocercal tails. 



LEPIDOSTEULE. Scales rhomboid, branchiostegal rays present, a pseudo- 

 branch, but no spiracle. Lepidosteus* garpike. AMIID.E, distinctly teleos- 

 tean in appearance with cycloid scales, amphicoalous vertebras, and heart 

 with reduced conus (fig. 596, B). Amia* bow fin. 



Sub Class III. Teleostei. 



The teleosts owe their name to the extensive ossification of 

 the skeleton, which consists, in the trunk, of amphicoelous vertebrae, 

 and in front a skull with numerous primary and secondary bones, 

 already enumerated (p. 560, fig. 589). Maxillaries and premaxil- 

 laries are present, but these are frequently without teeth, since 

 other bones of the mouth (vomers, palatines, liyoid, gill arches, 

 superior pharyngeals the latter alone in Cyprinoids) may bear 

 teeth. Frequently there are present small bones, usually forked, 

 lying in the intermuscular septa above the ribs, which are not pre- 

 formed in cartilage. These are the epipleurals, and are distinct 

 from the ribs. In the fins both cartilage and dermal rays are ossi- 

 fied, the former remaining small, the rays forming most of the 

 support. These rays may either be soft and flexible (Malacopteri) 

 or hard and spine-like (Acanthopteri), a matter of classificatory 

 value. In the first case they consist of numerous small threads 



FIG. 602. Perca fluviatilis. (From Ludwig-Leunis.) A, anal fin ; B, ventral fin; Br, 

 pectoral fin , K, operculum ; JV, nostrils ; R\, R^, spinous and soft dorsal fins ; tf, 

 caudal fin ; 67, lateral line. 



(fig. 602, Br, A, B, R z ), in the other the parts of a ray are fused 

 to a spine which, sometimes provided with poison glands (Scorpcena, 

 Amphacantlie, etc.), become good defensive weapons. The tail is 

 usually homocercal; the diphycercy of eels and other fishes is sec- 

 ondary. The dermal skeleton consists of ctenoid or cycloid scales, 

 sometimes of spines or body plates. In rare instances the skin is 

 naked. 



