NEW GENUS AND SPECIES OF THEROMORPHA 



557 



supraoccipital and supraoccipital, in addition of course to the par- 

 occipitals, exoccipitals, and petrosal, but I can find no evidence 

 whatever for the inclusion of the first-mentioned bone in the com- 

 plex. I have sectioned vari- 

 ous specimens, and studied 

 numerous others. If, then, 

 these bones correspond — and 

 they surely do— there are 

 no dermosupraoccipitals in 

 Dimetrodon, or they have 

 been reduced to the merest 

 vestige, as in the modern 

 gavials. As will be seen by 

 the figure (Fig. 4, po) the „ r,- . j /-,••. 1 i 



o \ o -r; r / ^ Pj(j_ 2. — Dimetrodon. Occipital complex, 



surface of the supraoccipital obliquely from behind. 50, supra-occipital; /)02, 

 articulating with the pari- proatlantal zygapophysis; po, paroccipital; st, 

 etals above is cartilaginous, '^^P^'^ ^' tabulare; bo, basioccipital condyle; 



eo, exoccipital; half natural size. 



corresponding to the condi- 

 tion found in the dinosaurs, crocodiles, lizards, etc. The exoccipi- 

 tals in Mycterosaurus sur- 

 round the foramen 

 magnum and are loosely 

 attached, as in Dimetrodon. 

 From below, not much is 

 visible. The descending 

 process of the paroccipital 

 for the stapes is visible 

 from behind, but I do not 

 discover either the stapes 

 or the tympanic, both of 

 which are present in 

 Dimetrodon (Fig. 4, t, st). 

 This last figure is intro- 

 duced here anticipatory of 

 a full discussion of the 

 cranial anatomy of this 

 and other genera, which will be published later. 



Fig. 4. — Dimetrodon. Occipital complex, 

 view opposite to that of Fig. i. ps, parasphe- 

 noid; bp, basipterygoid process; bs, basisphe- 

 noid; bo, basioccipital; st, head of stapes; 

 /, tympanic; ta, articular pit in paroccipital for 

 tympanic; a;-;!, articular surface; ^0, paroccipital. 



