SECOND SUB-CLASS— TELEOSTEI. 



Seart with a non-contractile iulhus arteriosus; intestine 

 without spiral valve ; optic nerves decussating ; sheleton ossified, 

 with completely formed vertebrm ; vertebral column diphycercal 

 or homocercal ; hrandhim free} 



The Teleostei form the majority of the fishes of the present 

 fauna, and are the geological successors of the Palaeichthyes, 

 undoubted Teleostei not ranging farther back than the 

 Chalk. This sub-class comprises an infinite variety of 

 forms; and as, naturally, many Ganoid fishes lived under 

 similar external conditions, and led a similar mode of life 

 as certain Teleostei, we find not a few analogous forms in 

 both series : some G-anoids resembling externally the Teleos- 

 teous Siluroids, others the Clupeoids, others the Chsetodonts, 

 others the Scombresoces, etc. But there is no direct genetic 

 relation between those fishes, as some Naturalists were in- 

 clined to believe. 



The Teleostei are divided into six orders : — 



A. AcANTHOPTERYGii. — Part of the rays of the dorsal, anal, 

 and ventral fins not articulated, spij^es. The lower pharyngeals 

 separate. Air-bladder, if present, without pneumatic duct in the 

 adult. 



B. ACANTHOPTERYGII PHARYNGOGNATHI. — Part of the rays 

 of the dorsal, anal, and ventral fins not articulated, spines. The 

 lower pharyngeals coalesced. Air-bladder without pneumatic duct. 



1 See p. 97, Fig. ^ and p. 152, Fig. 68. 



'. ^ and 



