574 



CHORD AT A. 



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

 fied opisthoccelous vertebrae and diphy- or homocercal tails. 



Lepidosteid^. Scales rhomboid, branch iostegal rays present, apseudo- 

 )>ranch,but no spiracle. Xe^jicZo.s^g^w,* garpike. Amiid^, distinctly teleos- 

 tean in appearance with cycloid scales, amphico5lous vertebrae, and heart 

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



Sub Glass III. Teleostei. 

 The teleosts owe their name to the extensive ossification of 

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

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

 already enumerated (p. 500, 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, 

 su|)erior 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 fiexible (Malacopteri) 

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

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



Fio. 603.— Peifd fluvtatili.i. (From Ludwig-Lpunis.) A, aual fin ; B, veutral fln : Br, 

 pectoral fln , A', operculum; X. nc^strils ; E,. Kj, spiuous and soft dorsal flns ; S, 

 caudal fln ; SI, lateral line. 



(fig. 002, IJr, A, B, R,X in the other the parts of a ray are fused 

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

 AiiipJuican/he, etc.), become good defensive weapons. The tail is 

 usually homocercal ; the diphyecrcy 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 . 



