62 0. G. Marsh— New Belodont Reptile. 



the latter genus are different from those of Belodon. Figure 1 

 shows the skull of Dijplosaurus., a crocodilian from the Jurassic 

 of Colorado. The superior nasal aperture {a) is in front, as in 

 existing crocodiles, while in the Belodonts^ as shown in figures 2 

 and 3, these openings are far back in the upper part of the skull. 

 Figure 2 represents a new species, found bj J. B. Hatcher in 

 the Triassic of ^N^orth Carolina. In this specimen, the quadrate 

 slopes forward, and not backward as in the Crocodilia. 



Other fossils of apparently the same group have been found 

 in Pennsylvania, and described by Lea under the generic name 

 Centemodon, and by Leidy, as Omosaurus. Still others 

 were described later by Cope, from both Pennsylvania and 

 ISTorth Carolina, and more recently some from the Triassic 

 of ISTew Mexico, which received the names Typothorax and 

 EpisGoposaurus. Nearly all the above specimens are so frag- 

 mentary that it is at present difficult, if not impossible, to 

 determine their exact relations to each other. 



The difficulty in this case is practically the same as that 

 which has occurred time and again in separating fossils found 

 together at other localities, especially where genera of reptiles 

 have been based upon isolated teeth, which, unlike those of 

 mammals, have so often proved unreliable. In the original 

 locality of Belodon^ near Stuttgart, in G-ermany, remains of 

 carnivorous Dinosaurs {Zanolodon) also occur, while Labyrin- 

 thodonts are still more abundant^ all represented by species of 

 approximately the same size. The fragmentary remains of 

 these, when mixed together, have led to much confusion, as the 

 many names proposed for them demonstrate. After various 

 well-preserved specimens were studied, the separation of the 

 Labyrinthodonts, even in isolated remains, became a compara- 

 tively easy matter, but the Belodon ts and Dinosaurs, being 

 more nearly allied, have hardly yet found their proper places. 



Precisely the same thing occurred when the rich J^orth 

 Carolina localities of nearly the same horizon were first 

 explored. The Belodonts, Dinosaurs, and Labyrinthodonts 

 were all there, with their fragmentary remains commingled in 

 a still more indiscriminate manner. This was in part true, also, 

 of the Pennsylvania localities, and those in '^qw Mexico have 

 likewise contributed their share to the general confusion. The 

 discovery of more perfect specimens will doubtless gradually 

 remove the obscurity now existing as to the strange vertebrate 

 fauna of this extensive horizon. 



Yale University, New Haven, Conn., June 5, 1896. 



"Explanation of Plate I. 



Impression of dermal armor of Stegomus arcuatus, Marsh. One-third natural 

 size. From the Triassic sandstone. New Haven, Conn. 



