ACCOUNT OF A GANOID FISH FilOM QUEENSLAND. 265 
from the heart by two valves opposite to each other. Nor is 
this the only distinguishing chaiaeter. A heart with a true 
conus arteriosus is always accompanied by a more or less deve- 
loped spiral valve of the intestine (entirely absent in Teleos- 
teans), and by non-decussating optic nerves. The fore and hind 
limbs of the Chondropterygians are also paddles supported by 
a cartilaginous framework ; the tooth-bearing pterygo-palatine 
arch of the Dipnoi is homologically identical with the 66 upper 
jaw” of a shark. And the anotomical evidence in favour of a 
union of Ganoids and Chondropterygians is rendered complete 
by the Holocephala (Chimaeras), which differ in several import- 
ant points from the other Chondropterygians, approaching the 
Ganoids by these very characters, and are, in fact, an inter- 
mediate form. They are sharks in external appearance and 
with regard to the structure of their organs of propagation. On 
the other hand, there is only one external gill opening on each 
side ; the skeleton is notochordal, and the palatal apparatus 
coalesces with the skull as in Dipnoi , which is not the case in 
any of the sharks and rays ; likewise the dentition approaches 
that of Ceratodus . Sir Ph. Egerton has drawn attention to 
another very important fact ; viz. that the dorsal spine is arti- 
culated to the neural apophysis, and not merely implanted in 
the soft parts and immovable, as in sharks. Furthermore, all 
those modifications which show an approach of the ichthyic 
type to the Batrachians are found in Ganoids and Chondrop- 
terygians, none in Teleosteans; and, finally, the coexistence and 
development of Ganoids and Chondropterygians in geological 
epochs when no (or only very few) Teleosteans existed, is a 
circumstance which seems to confirm a conclusion arrived at 
from an anatomical point of view only ; namely, the conclusion 
that Ganoids and Chondropterygians should be united in one 
sub-class — Palceichthyes. 
3. A third point of the deep interest is the great antiquity 
of the Dipnoous type. At the commencement of these notes 
we have seen that there is no evidence to show that the 
Barramunda is even generically distinct from those fishes, of 
which, unfortunately, the teeth only have been preserved. But 
some of the oldest fishes, known from the Devonian epoch, and 
designated by the names Ctenodus and Dipterus , prove to be 
Dipnoous fishes. They had the same dentition as Ceratodus , 
nostrils within the mouth, acutely lobed paddles, a notochordal 
skeleton, and, with exception of dermal scutes, a very similarly 
formed skull. Thus, then, we have the following facts before 
us : The Dipnoous type is represented in the Devonian and 
carboniferous epochs by several genera ( Dipterus , Ctenodus , 
Chirodus , Conchodus , Phaneropleuron) ; it is then lost down 
to the Trias and Lias, where the scanty remains of a distinct 
