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POPULAR SCIENCE REVIEW. 
paired “ branchial 55 fins, so characteristic of true fishes, but 
only those pairs of locomotory organs which are homologous with 
the limbs of higher vertebrate animals, namely, the “ pectoral” 
and u ventral ” fins. 
Even in the Crossopterygidse ( Osteolepis , &c., and Polyp- 
terus ), which present some affinities with Geratodus , dorsal and 
anal fins are present. The double air-bladder of Polypterus 
only approximates to the reptilian-like lungs of Geratodus 
and Lepidosiren, It is worthy of remark that Professor Owen, 
whilst retaining the Protopteri with the Fishes, prints against 
the order the significant word 66 ( Transitional ”).* 
Dr. Melville, who devoted careful attention to Lepidosiren 
annectens , in 1847, | regarded it as a true Amphibian . For this 
conclusion he relied on the absence of the supra- occipital bone, 
the presence of the large epi- and basi-cranial bones, the non- 
development of the maxillary and inter-maxillary bones, and 
especially the enormous development of the Wernerian bones, 
which become subservient to mastication and are anchylosed to 
the expanded pterygoids ; on the nostrils being double ; on the 
existence during the adult condition of external cutaneous 
gills which do not occur in any fish; and on the coexistence 
of external and internal gills, with lungs : in other words, on 
its exhibiting the different modes of circulation, respiration, 
&c., observable in the second stage of the larva of the frog, 
and in Amfehiuma or Menopoma , &c. 
In the Amphibia of the order Labyrinthodontia, of the 
Upper Coal period, one genus at least, Archegosaurus (though 
probably there are others besides), has the notochord per- 
sistent, the vertebral arches and peripheral elements only 
being ossified: it is covered with small narrow sub-ganoid 
scales, and there are traces of branchial arches. The skull in 
its combined dermo-neural ossification resembles that of the 
Sturgeon and of Polypterus , &c. (Owen.) 
In the Amphibia of the order Ophiomorpha, branchial 
clefts and rudimentary branchial filaments have been observed. 
These strange snake-like amphibians have transverse rows of 
“ cycloid ” scales imbedded in their integument. When adult 
respiration is carried on by lungs ; the vertebrae are amphi - 
coelian^. a character common to most fishes and to some 
reptiles. 
Referring to the Amphibia, Professor Huxley observes, they 
“ are distinguished from the Sauropsida and Mammalia by very 
* Owen, “ Comp. Anat. Verteb.” 1866, Vol. i. p. 14. 
t A. G. Melville, on the Lepidosiren, in Report of Brit. Assoc. Adv. 
Sc. 17th Meeting, 1847, Transact. Sect. p. 78. 
\ Hollow at both ends. 
