108 ON THE STRUCTURES AND DISTRIBUTION OF THE 



This family was characterized by Dr. J. E. Gray, in Proc. Zoological Soc. London, 

 1858, 142. 

 VIII. Prefrontals and pterygoids present. 



Parietals not embracing the broad frontals. 



Orbitosphenoid 



No dcntigerous plates on the parasphenoid bone. 



A postfronto-squaraosal arch, sometimes ligamentous. 



Carpus and tarsus osseous. 



Vertebrae opisthocoelian. 



Occipital condyles sessile. 



Pleueodelid/E. — Genera Hemisalamandra, Neurergus, Lissotriton, Lophinus, 

 Euproctus, Cynops, Notophthalmus, Pleurodeles, Glossolega, Siranota. Regio Pate- 

 arctica ; three species in North America. 



These genera form a series. measured by the increasing strength and ossification of 

 the post-frontoparietal arch, which has been pointed out by Gray and figured by Ger- 

 vais, Dumeril, and Duges. It is first bony in Lophinus : in Glossolega it is very 

 stout, and leaves but a small crotaphite foramen, while in Siranota it fills up the 

 foramen, being entirely continuous with the parietal bone. On this ground Dr. 

 Gray has regarded this genus as representing a familj^, — " Siranotida^," — but it does 

 not appear to be more different fi'ora Glossolega than the latter is from Neurergus 

 and Hemisalamandra.* 



The study of the Mammalia, the Rapaciou^ Pullastrine, Gallinaceous and Passe- 

 rine Birds, of the Sauria, Tortoises, Tailless Batrachianst and Malacopterygian 

 Fishes, leads to the conclusion that these portions of the Fauna Neotropica represent 

 much lower stages in their respective series than do the same types in the Regio 

 Palseotropica. In a few types, as Zygodactyl Birds and Ophidia, there is, as far as 

 our present knowledge extends, a seeming equivalency ; but in no single group can a 

 superiority be proven for the Fauna Neotropica; the tests of the grade being ever 

 the retention of the characters of the incomplete stages of the extremes of the series, 

 the relations of generalized and specialized structure, or, where we have not yet demon- 

 strated thoroughly, by the affinities with forms whose relations in these respects are 

 known. These relations coincide in kind with those contrasting the Faunae of earlier 

 and later geological periods, but not in degree, since tliey refer to the sttjbordinate or 



* The genera adopted arc those arranged by me, Proo. Acad. 1862, 343. The preparations on which the 

 preceding investigations have been made are the collections of Prof. Baird and myself; the former in the 

 Museum of the Smithsonian Institution, Washington. 



t This is in opposition to the following proposition of (lUnther, (Proc Zool. Soc. Lond., 1858,) the contrary 

 of which, I think, has been abundantly proven. He says: " Such a difference between the animal life of the 

 New World and that of the Old as pertains to other parts of the animal l<ingdom, is not to be observed in the 

 Batrachians. Dissimilarity and similarity of the Batrachia Fauna depend upon the zones." 



