VERTEBEATA. 409 



II. Gnathostomata. 

 a) Auamnia. 



1) Pisces. 



Selachii. 

 Squali. 



Hexanchus, Heptanchus, Acanthias, Scjmnus, Galeus, Scyllium, 

 Squatiua. 

 Raj re. 



Raja, Torpedo, Trygon. 

 Holocephali. 



Chimsera. 

 Dipnoi. 



Monopneumones. 



Ceratodus. 

 Dipneumones. 



Protopterus, Lepidosiren. 

 Ganoidei.* 

 Sturiones. 



Acipenser, Spatularia. 

 Polypterini. 

 Polypterus. 

 Lepidosteini. 

 Lepidosteus. 

 Amiadini. 

 Amia. 

 Teleostei. 



Physostomi. 



Abdominales. 



Clupea, Salmo, Esox, Cyprinus, Silurus, Mormyrus. 

 Apodes. 



Mursena, Conger, Gyniuotus. 

 Physoclysti. 

 Anacanthini. 



Gadus, Pleuronectes. 

 Pharyngognathi. 



Belone, Hemirhamphus, Chromis, Labrus. 

 Acanthopteri. 



Perca, Labrax, Trigla, Scropajna, Anabas, Mugil, Scomber, 

 Zeus, Trachypterus, Gobius, Cyclopterus, Blennius, 

 Lophius. 

 Plectognathi. 



Ostracion, Diodon, Orthagoriscus. 

 Lophobrancliii. 



Byngnathus, Hippocampus. 



2) Amphibia.t 



TJrodela. 



Perennibranchiata. 



Siredon, Menobrancliua, Proteua. 

 Caduci branch lata. 



* I regard each of these divisions of the Ganoidei as highly independent. They 

 represent the last shoots of very divergent series of forms, of which that of the Polyp- 

 terini has many points of relationship to the Dipno'i ; the Amiadaj, on the other hand, 

 are the nearest allies of the Teleostei (Clupeida?). It would, perhaps, bo best to 

 separate them completely from the Ganoidei. The Sturiones show the greatest 

 resemblance to the Selachii. 



I must regard the Selachii as being nearest to the ancestral form of the Gnathosto- 

 matous Vertebrata. The Holocephali, as well as the Dipnoi and Ganoidei, appear to 

 have branched off from them, while the Teleostei again are a branching off from the 

 Ganoidei. 



t The living Amphibia form only a very small group, which in many parts indi- 

 cate considerable retrogression ; but few fossil forms can be safely placed in it. The 

 paleeontological records of the Amphilsian phylum are fragmentary in the highest degi-ee. 

 There are many reasons for placing the Ai-chegosauria with them, but yet there are 

 many points in which these forms resemble the Keptilia. 



