DIPNOL 573 
The Teleosts include the great majority of living fishes, which 
are classified in thirteen sub-orders and numerous families, ¢.g. 
Clupeidee (herrings); Salmonide (salmon, trout); Cyprinidze 
(carps) ; Murzenidze (eels); Esocidee (pike); Gasterosteide (stickle- 
backs) ; Syngnathidze (pipe-fish and sea-horses) ; Gadidze (cod-fishes) ; 
Percidee (perch) ; Scombridze (mackerels) ; Pleuronectidse (flat-fishes) 5. 
Cottidee (bull-heads) ; Triglidee (gurnards) ; Lophiidz (anglers) ; 
Tetrodontidz (globe-fishes). 
Sub-Class III. Drpnor. ‘ Mud-Fishes” 
Fishes with a lung—the modified swim-bladder—as well 
as gills ; the paired fins are of the archipterygium type, with 
a long segmented axis, sometimes bearing a series of lateral 
pieces on each. side, with overlapping cycloid scales, with’ 
multicellular skin-glands, with a diphycercal tail. The 
notochord persists, and its sheath is unsegmented ; the skull 
is autostylic and is largely a persistent chondrocranium with 
the addition of some membrane bones; there are large 
compound grinding teeth. The external nares are on the 
ventral surface of the snout, or even within the upper lip, 
and the arching over of the nasal grooves leads to the 
formation of separate internal nares. The heart is 
incipiently three-chambered, containing mixed blood, with 
a spiral conus arteriosus with numerous valves; there is a 
vein resembling the inferior vena cava of higher vertebrates. 
There is a spiral valve in the intestine. The eggs are large 
and exhibit total unequal segmentation, as in Amphibians. 
The Dipnoi, whose name means double breathers, are 
now represented by three genera—Ceratodus, from two. 
rivers of Queensland; /votopierus, from certain African 
rivers, e.g. the Gambia; and Lefidosiven, from the Amazons. 
The wide distribution is noteworthy. 
They are very ancient forms, for Ceratodus existed in 
Triassic and Jurassic times (though no _ post-Jurassic 
remains are known). There were also undoubted Dipnoi 
far back in Paleozoic times, such as Dypterus and 
Phaneropleuron of the Devonian, Cienodus and Uronemus 
of the Carboniferous. 
The living Dipnoi are probably the survivors of an 
archaic. group; in their teeth and autostylic skull they 
resemble Holocephali; in their fins and air-bladder. they 
