J. K. Thiieher — Median and Paired Fins. 298 



tiler's denoraiiiation, tlu'ii, of tlie ultiniato and ])eiiultimate joints of the 

 neural S])ines of Ceratodas as " interneural first" and " interneural 

 second," is ill chosen, and rests on a mistake in homology. That 

 great genetic group, then, consisting of Dipnoi, Amphibia and Am- 

 niota, seems to have entirely lost those primordial median fin-rays 

 which appeared so early and are found even in Mxjxine. 



Limb-skeleton of Air breathing Vertebrata. 



In 1864, Gegenhaur* set forth the splendid results of a widely 

 extended investigation of the limb-skeleton of the air-breathing 

 vertebrates. Herein was established the typical form of these parts 

 for this large gi'oup, consisting of Amphibia and Amniota. Inasmuch 

 as there is no doubt of the natural, that is the genetic, character of 

 this group, and inasmuch as it is marked out from all other vejte- 

 biates by the development of a fenestra ovalis and the modification 

 of the proximal part of the second post-oral, or hyoid, arch into a 

 stapes in connection therewith, I ventui'e to use the name Stapedifera 

 in place of the circumlocutory air-breathing Vertebrates. For the 

 Stapedifera, then, the typical limb-skeleton was established ; typical 

 in the sense of the older anatomists, as that ideal form from Avhich 

 we could in our minds easily derive the various actual forms now 

 living ; but typical also in the newer sense, as that actual form, the 

 limb-skeleton of the latest common ancestors of all Stapedifera, from 

 which have been developed the corresponding parts in all living 

 Stapedifera. 



The same form belongs to both fore and hind limbs. Using the 

 names applicable to the former, we have, as is well known, humerus, 

 radius and ulna, radiale, intermedium and ulnare, a centrale, and 

 then set around these, five cai'palia followed by their metacarpals 

 and phalanges. Moreover, the strong suspicion of the double nature 

 of the centrale, as evidenced in the descriptions of Cryptobranchns 

 JaponiGus.\ by Schmidt, Goddard, and J. Van der Hoeven, is later, 

 1865, confirmed by the careful observations and clear presentation 

 of the anatomy of that animal by Hyrtl.J; The Ichthyosaurs§ and 



* Gegenbaur, Untersuchungen zur vergleichenden Anatomie der Wirbelthiere, 

 Hft. 1, Carpus imd Tarsus. 



f Gegenbaur, Unters., Hft. 1, p. 57. 



\ Hyrtl, Schediasma anatomicum. 1865. Gegenbaur, Unters., Hft. 2, p. 165. 



§ Gegenb., Unters., Hft. 2, p. 165, and Jena Zeitschr., Bd. v, Hft. 2, 1870. Gegen- 

 baur, Ueber das Gliedmaassenskelet der Enaliosaurier. In this last a furtlier modifi- 

 cation is made in tlie recognition of the pisiform as the remains of a sixtli row, an(] 

 as being an essential part of the carpus and not merely a sesamoid bone. 



