76 



G. J. de Fejervaiy: 



dermal plates themselves. That means that the crusta 

 calcarea overroofing the skull in some Batrachians and 

 Reptiles,!*) in a similar way as in Pelohates or Ceratophrys for 

 instance, is morphologically equivalent, i. e. homologous 

 with the whole of any secondary dermal bone-plate of 

 the body, the difference between their mode of occurrence, i. e. 

 their independency from or connexion with the endoskeleton, being 

 simply retraceable to the above mentioned aberrant topo- 

 graphical conditions. 



With respect to the phylogenetical development of the secon- 

 dary exoskeleton we can distinguish, as within each Evolution, a 

 phase of ascension and a phase of culmination, which are then often 

 followed by a third phase, represented by degeneration. There is no 

 dif f iculty to approximately establish the phase of culmination, but to 

 decide whether certain characters of an organism are developing 

 or degenerating, may be, in some cases, a very hard task. 



P. cultripes is, with respect to its secondary dermal ossifica- 

 tions, surelyin the phase of culmination, whilst the application of 

 the biogenetical law allows the supposition that the secondaiy 

 dermal ossifications of P. fuscus are not, as Prof. Abel^^) seems to 

 presume, in the phase of degeneration, but, on the contrary, in that 

 of ascension. It remains naturally an open question whether this 

 Speeles will ever reach, or not, the same culmination as P. cultripes. 



The rugged bony Stratum covering the skull in Hemiphractus 

 and some other Tailless Batrachians belongs also to the category 

 of secondary dermal ossifications, even if it were inherited from 

 Stegocephalian ancestors, as supposed by Boas. 



If, however, as I presume, the ontogeny of these forms would 

 prove that the secondary dermal ossification appears also in these 

 cases as late as in Pelohates, and if the skull of the young animal 

 would present also here the typically specialized anurous 

 features of the frontoparietals, tympanic and other bones, — and 

 I am afraid that future investigations will prove it to be so — 

 Mr. Boas' mentioned supposition ought to be decidedly rejected. 



Let US now examine the Reptile s. With respect to the 

 absence or presence of a secondary exoskeleton the youngest 

 Order, the Lacertilia, offer the most manifest conditions. Thus 

 we shall begin with the examination of the latter ones. Within this 

 Order we may distinguish two main Types. The first is re- 

 presented by forms in which the body is generally devoid 

 of exoskeletal plates, the roof of the skull, i. e. the surface 

 of its primary dermal bones, is generally smooth, and the Upper 

 surface of the Orbits is not prötected by a lamina supr aciliaris. 

 Such conditions are present in the Varanidae, Agamidae, &c. 

 I will designate this Type as the nudorbital. The second main 

 Type is represented by forms in which the body very often bears 



Cfr. HeJoderma, Ophisaurus, Trachysaurus, Tiliqua, &c. 

 op. cit. p. 314. 



