4 PEOCEEDINGS OF THE ISTATIOZSTAL MUSEUM vol.73 



fact allows the suggestion that the dentation may have been acrodont 

 in character. 



None of the sutures on the internal side of the jaws can be detected, 

 rendering it impossible to differentiate the elements. Meckel's 

 groove is prominently developed and leads back to the enlarged 

 cavity in the swollen part of the jaw. It would seem that the for- 

 ward part of this groove was open and that it was not covered by the 

 splenial as in many reptiles. There seems to have been a small sub- 

 circular internal mandibular foramen at a point immediately oppo- 

 site the coronoid section of the jaw. (See fig. 1.) A slight indenta- 

 tion immediately forward of the midlength of the ramus on the inner 

 side strongly suggests the presence of a second but smaller foramen. 



The unusual height of the mandible as a whole, its relatively short 

 surangular, receding chin, and transversely swollen portion posterior 



to the middle are all features found in the 

 jaw of the cotylosaurian reptile Diadeetes, 



Measurements 



Millimeters 



Greatest length of mandible 46. 5 



Greatest width across center of symphysis^ 14. 5 



Greatest width across posterior ends of 



Fio. 2. — Hyfsognathus pen- ,.„,.,,• aq k 



_ rami 4o. o 



NEBIj NEW SPECIES. TXPB, 



Cat. No. 11643, U.S.N.M. Greatest depth of mauulLio at eeuier +12.5 



antehioe (1) DORSAL VERTE- Greatest width of postcornoidal part 13.0 



BRA. Viewed FROM THE AN- Greatest width at center of ramus 7.3 



TERIOR END. NaTDEAL SIZE. 



Drawn from a cast made Vertebrae. — Evidence is found showing 



the presence of at least 17 presacral verte- 

 brae, but none is sufficiently well preserved 

 to show the complete details of structure. Those immediately pos- 

 terior to the lower jaws are widely scattered, but the remaining parts 

 of the vertebral column were in articulated series, except for a short 

 gap near the posterior end of the slab. 



The centra are deeply amphicoelous and may have been noto- 

 choidal, though there is lack of positive evidence of this last sugges- 

 tion. Neither do I find any evidence of the presence of intercentra. 

 The zygapophyses are of good size and have the articulating planes 

 horizontal as in Seymouria and Telerpeton. The mold of a vertebra 

 lying on its posterior face, immediately posterior to the right ramus 

 (pi. 3) serves to illustrate the great conical concavity of the centra. 

 Furthermore it shows the relatively large size of the neural canal, 

 the high arch, and the general heaviness of the vertebra as a whole 

 as shown in Figure 2. From its position in relation to the rest of 

 the skeleton I am led to the conclusion that it pertains either to the 

 posterior cervical or the anterior dorsal region. 



FROM THE NATURAL MOLD IN 

 THE ROCK 



