190 BULLETIN 34, UNITED STATES NATIONAL MUSEUM. 



DESMOGNATHID^. 



Cope, Journ. Ac. Nat. Sci. Phila., 1866, 107. 



Pterygoids wanting. Orbitosphenoid separated by membrane from 

 prootic. Vestibule, internal wall osseous. Dentigerous plates on the 

 paraspbenoid. Ceratobyal articulating witb quadrate. Carpus and 

 tarsus cartilaginous, VertebrsB opistbocoelous. Hyoid apparatus as 

 in tbe Pletbodontidse. 



Tbe peculiarity of the vertebrae distingnisbes this family chiefly from 

 the last. In the only genus which represents it, there are numerous 

 peculiarities, which are not found elsewhere. Should other genera be 

 found which do not possess them, the above diagnosis would probably 

 be the proper test of their family affinities. 



The distribution is confiued to the eastern district of the nearctic 

 realm so far as yet known. 



The Thoriidse only differ from the Desmognathidai in the osseous 

 carpus and tarsus. The single genus Thorius Cope is included by 

 Boulenger in the Desmoguathida3. Thorius has a boletoid tongue like 

 Spelerpes, and the parietal region mostly membranous. Toes, 4-5. One 

 species, T.pennatulus Cope, of small size, from E. Mexico. 



DESMOGNATHUS Baird. 



Joui-u. Ac. Mat. Sci., i. 282,285 ; Gray, Cat. Brit. Mus., 1850, 40 ; Cope, 

 Proceed. Ac. Phila., 1869 112 ; Strauch, Salam., p. 72 ; Boulenger, 

 Cat.Batr. Sal. Brit. Mus. ed.ii, 1882, p. 77. 



Premaxillaries united, embracing a fontanellej parietal bones ossi- 

 fied. Prefrontal bones wanting. Occipital condyles on cylindric ped- 

 estals. Temi>oral muscle arising only from the atlas, with a tendinous 

 external margin and insertion, passing freely over the parietal and 

 prootic bones. Tongue attached, except by its lateral and posterior 

 margins. Vomerine and sphenoidal teeth present. Digits distinct, 4-5. 



The absence of o. prefrontale does not appear to be the result of its 

 confluence at any late period with the nasale; its ordinary position is 

 traversed by the frontal suture. The frontal bone is decurved, and 

 closes the preorbital aspect of the superpalatal vacuity, usually open. 



This marked genus, so abundantly represented by individuals in tlio 

 eastern district of North America, is not admitted by either Dumeril 

 orHallowell, probably because it do3S not differ in external characters 

 from Plethodon. It is an excellentilhistration of the error of adhering to 

 external characters only, in the explanation of the relations and affinities 

 of organized beings, except for a limited range. The examination of 

 the skeleton of species of this genus utterly changes the impressions 

 produced by a consideration of the external characters. It maybe 

 stated as characteristic of the Batrachia in general that their affinities 

 can not be determined without study of the skeleton. 



