EXTINCT BATRACHIA. 355 



consolidated into a single vertical mass ; ilium attached immediately to 

 sacral vertebrae ; proximal tarsal bones elongate. 



The extinct genera belong for the greater part to the order Stego- 

 cephali. The order Stegocephali is evidently distinct from all others of 

 the class. The supraoccipital bone is not present in any other order of 

 Batrachia. The presence of the epiotic bone, which I have verified on 

 a number of American genera, and which has been pointed out by Euro- 

 pean authors in genera discovered in that continent, is a character which 

 is only shared by the order Proteida. In the Trachystomata the position 

 of this element is occupied by a great backward prolongation of the pro- 

 otic, which is an exaggeration of the peculiar structure characteristic of 

 the living Batrachia of the orders Urodela and Anura. The additional 

 bones covering the temporal fossa, called by Owen the postorbital and 

 supratemporals, do not exist in any of the other orders. None of the 

 genera present any of the distinctive features of the Anura, unless, in- 

 deed the single genus Pelion have the united ulna and radius of the 

 frogs, a point yet somewhat doubtful. With the Urodela the relations 

 are closer, but the structure of the posterior part of the skull is here the 

 same as that of the Anura. The same remarks will apply to the Coscilias, 

 whose resemblances to the Stegocephali are superficial only. No forms 

 certainly related to the Trachystomata have been discovered in any Ameri 

 can formation, and one, the Palseosiren Brinertii, Geinitz, has been found 

 in Europe. 



There are some relations to classes outside the Batrachia suggested by 

 the osteology of this order. Thus the relations of the parietals, occipital 

 and epiotic, are almost exactly those characteristic of many of the phy- 

 sostomous bony fishes, as Cyprinidse, Characinidas, Amiidas, etc., or super- 

 ficially, as in Lepldosteidse and Polypteridie, where the supraoccipital is 

 represented by dermal ossifications. The relation to these forms is closer 

 than to the Dipnoi. In the opposite direction a distant approach to the 

 Ichthyopterygia may be observed in a few points. As in other reptiles, 

 the occipital series of bones is complete in this order, but the epiotic is 

 not well distinguished. The squamosal bone is produced downward on 

 the quadrate more than in reptiles generally, thus resembling slightly 

 the Batrachia, and the supratemporal, already described as peculiar to 

 Stegocephali in their class, only exists among Ichthyopterygia among rep- 

 tiles, and, as in the former, unites with a postorbital bone to form the 

 supratemporal roof. The grooved teeth of the Ichthyopterygia may be 

 considered in the same connection, as well as the extension of the squa- 

 mosal over the deeply-inclosed quadrate bone in the Crocodilia. 



The order Stegocephali, as here adopted, was proposed by the writer in 



