TELE OS TEL 551 



A. huso of Southern Russia may measure 25 ft. and weigh nearly 

 3000 Ib. ! Most of the species are found both in the sea and in rivers 

 or lakes. The roes or ovaries form caviare ; the gelatinous internal 

 layer of the swim -bladder is used as isinglass. 



The genus Scaphirhynchiis is represented in Asia and the United 

 States ; Polyodon or Spatnlaria spatula is the paddle-fish or spoon-bill 

 of the Mississippi. 



Order 3. HOLOSTEI ! with bony skeleton. 



Living examples : Lepidosteus and Amia. 



Extinct examples : Lepidotus, Pycnodus, Aspidorhynehus. 



The N. American bony pike Lepidosteus is covered with 

 rows of " ganoid " scales ; the whole skeleton is well 

 ossified, and the vertebral bodies are opisthoccelous ; the 

 swim-bladder is like a lung in structure, and to some 

 degree in function. The bow fin, Amia calva, frequenting 

 still waters in the United States, has a similar lung-like 

 swim-bladder. 



Order 4. TELEOSTEI. The " Bony Fishes." 



This order includes most of the fishes now alive. 

 Though comparatively modern fishes, they are older than 

 was formerly supposed, as several Jurassic genera ( Thrissops, 

 Leptolepis,okc.\ which used to be classed as "Ganoids," 1 must 

 be considered as actual Clupeoids, or herring-like Teleostei. 

 It is, however, not until the Upper Cretaceous and Tertiary 

 epochs that they assume among fishes that overwhelming 

 preponderance in numbers which they possess at the present 

 day. The physostomous type of Teleostean is the most 

 ancient, and probably stands in a continuous genetic line 

 with the Holostei. 



The skeleton is well ossified, with numerous investing 

 bones on the skull, others in the operculum, and on the 

 shoulder-girdle. There is always a supra-occipital in the 

 skull. The tail is sometimes quite symmetrical or 



1 The term " Ganoids," which we abandon, is often used to include 

 Crossopterygii, Chondrostei, and Holostei. Though they agree in 

 having a conus arteriosus with many valves, as opposed to the 

 Teleostean bulbus, an optic chiasma, as opposed to the decussate 

 condition in Teleosts, and an intestinal spiral valve which is absent in 

 Teleosls, they do not seem to form a natural division. 



