236 THE OSTEOLOGY OF THE REPTH^ES 



broad, short, with large pineal opening, and palate and coronoids 

 covered with conical teeth. Three sacral vertebrae. Texas. 

 Casea Williston, ? Trichasaurus Williston. 



E. SUBORDER Uncertain 



Family Paleohatteriidae. Small, slender reptiles. Twenty- 

 seven presacral vertebrae; three sacrals. Parasternal ribs present. 

 Intimate structure of skull unknown. Skeleton feebly ossified, prob- 

 ably young animals, the metacoracoids not ossified. Vertebrae 

 notochordal, ribs holocephalous. Lower Permian. 



Paleohatteria Credner, Germany. Haptodus Gaudry, France. 

 ? Callibrachion Boule, France. 



Incertae Sedis. MycterosaurusW\\\\s,ton,GlaucosaurusW\\\i'&tOTi, 

 Tomicosaurus Case, Metamosaurus Cope, Emholophorus Cope, Texas. 

 Archaeoholis Cope, Illinois. Aphelosaurus Gervais, Autun, France. 

 Stereorhachis Gaudry (? Sphenacodontidae), Autun, France. 



Doubtfully members of the order: Ammosaurus Huene (Triassic). 

 Datheosaurus. 



5. ORDER THERAPSIDA 



Less primitive, more upright-walking reptiles, the propodials more 

 or less inclined in locomotion. Vertebrae amphicoelous, rarely noto- 

 chordal, dorsal intercentra unknown. Palate and limbs less primitive ; 

 pelvis with larger pubo-ischiatic vacuity or thyroid opening. 



As stated on a previous page, sharp distinctions between the mem- 

 bers of this order and the preceding one cannot be made. The primi- 

 tive characters common to both orders are largely included in the 

 Synapsida. But the very great differences presented by the later, 

 Triassic, forms, especially those included under the Cynodontia, dif- 

 ferences as great as those between any other two orders of reptiles, 

 render a division or divisions imperative, even though it may result, 

 as is so often the case in other groups of animal and vegetable Hfe, 

 in the structural differences between members of the same group 

 being greater than those limiting the groups themselves. This 

 division, it seems to the writer, may be best made at the present 

 time between the Lower and Middle Permian types, that is, based 

 upon the stages of evolution chiefly. Perhaps when more is known 



