Actinopterygii Isospondyli. 



109 



mostly from the Lithographic Stone of Bavaria ; and these differ 

 from the herring's (Clupeidse) chiefly in the meeting of the 

 parietal bones and in the simple character of the tail. Lep- 

 tolepis (Fig. 154) is first represented by small species in the 

 Upper Lias of England, France, and Wiirtemberg. 



Either here or immediately after the " Amioids " (the 

 Pholidophoridee having previously been classed with the 

 " Lepidosteoids "), it has long been customary to recognize a 

 break in the series of Teleostomatous fishes. All groups below 

 have been united under the name of GAXOIDEI (enamelled-scaled 

 fishes) ; all above have been termed TELEOSTEI (bony-fishes). 

 This arrangement was very convenient so long as the extinct 

 families were more incompletely known ; but fossils now show 

 that it cannot be scientifically maintained, and the terms 

 " Ganoid" and " Teleostean " must thus be employed in future 

 merely in a general way for enamelled-scaled and modern bony 

 fishes respectively. 



Most of the so-called " Teleostean " fishes have a remarkably 

 developed internal skeleton, as may be perceived from the 



FIG. 155. Skeleton of the Common Perch. 



o, premaxillary bone; l>, maxillary bone; c, lower jaw; d, palatine arch: e, cranium; 

 f, interoperculum : <j g', vertebral column ; h, pectoral fin ; i, pelvic fin ; k, spinous 

 dorsal fin ; I, soft dorsal fin ; m, anal fin ; n, upper, and n', lower lobe of caudal fin. 



[The pectoral and pelvic fins each form a pair, and correspond respectively to the anterior 

 and posterior pairs ot limbs of the higher vertebrata. The dorsal, caudal ,and anal fins are 

 median and unpaired.] 



A. B. 



.Fie. 156. Scales of Teleostean Fishes. A, Cycloid ; B, Ctenoid. 



accompanying figure of that of the common perch (Fig. 155). 

 Very few are covered with bony scales, the large majority 



"Ganoid" 

 and "Teleos- 

 tean." 



