ON THE STRUCTUUE OF THE LABYRINTIIODONTS. 247 



would not be easy to frame an unexceptionable statement as to the zoological 

 position of the Labyrinthodonts. "Were they now alive, they wovild doubtless 

 be considered Amphibia. The double occipital condyle, the parasphenoid 

 ossification, and the presence of a branchial apparatus in the young or larval 

 state would overpower such considerations as the Crocodilian scutes or the 

 Crocodilian character of the exposed parts of the cranium. Eut in dealing 

 with a long extinct group we are not altogether justified in trusting simply 

 to those characters which suffice to define the classes and orders of existing 

 animals. On any theory of descent with modification there would thus be 

 danger of coordinating an extinct group with its own modified or difl^erentiated 

 descendants. Even if all such theories be discarded, it remains to be shown 

 that we can legitimately impose a division into Classes and Orders based on 

 the study of recent Yertebrates upon generic forms of Carboniferous or 

 Triassic age. 



Palteontologists have not not held themselves bound to refer every ancient 

 type to existing classes. The Labyrinthodonts were regarded by Goldfuss as 

 intermediate between Crocodilia and Lacertilia, afterwards as intermediate 

 between Ichthyoda (Perennibranchiata), Crocodilia, and Lacertilia. Burmeister 

 considers them to have affinity to all the orders of Amphibia (Amphibia + Eep- 

 tilia), taking the same view of the position of the Trilobita among Crustacea. 

 Now that the writings of Darwin have given greater definiteness and coherence 

 to such views of zoological relation, and have rendered it possible to regard 

 all natural history as a pedigree, speculation has become bold indeed. 

 Hteckel* is able to assure us that the Ganocephala diverged from the Peren- 

 nibranchiate Amphibia (which make the thirteenth step in the descent of 

 man) during the Carboniferous period, that they developed Proterosaurus and 

 the Labyrinthodonts (branches which soon died out), and that the Ganocepha- 

 lous line is continued down to our own day by the Gymnophiona. It is 

 hardly necessary to point to Hssckel's " Stammbaum " of the Ganoid Pishes and 

 the Dipnoi, which recent discoveries have done so much to impugn, in order 

 to inspire distrust of these " far-reaching Phylogenies." Speculation as to 

 the derivation of ordinal tj-pes, though undoubtedly legitimate, has hitherto 

 proved extremely hazardous. 



If we restrict ourselves to such statements as may be maintained by evi- 

 dence, we can at present say nothing more definite than this : — that the 

 Labyrinthodonts were in nearly all important respects like recent Amphibia ; 

 that their most striking peculiarities are those which adapted them for a 

 predatory life ; that certain species, or certain details of structure, recall 

 the recent Ilrodela, others the Gymnophiona, while the resemblance to the 

 Batrachia is hardly ever so close as to one or other of the lower orders of 

 existing Amphibia. 



Distribution. — Remains of Labyi'inthodonts have occurred in England, 

 Scotland, Ireland, Germany, Russia, Central India, South Africa, Australia, 

 and North America. In the British Museum and in the Museum of the 

 College of Surgeons undescribed specimens of Labyrinthodonts are pre- 

 served, which have -been obtained from the Rhffitic beds of the Severn. 

 One genus (BJiinosaun(s) has occurred in the Oolitic strata of the Govern- 

 ment of Simbirsk (Russia). It is there associated with Ichthyosauria and 

 Qrypliaa dilatata. 



* Schopfuiigsgeschichte, 2nd ed : compare pp. 524, 580, and tab. xii. 



