114 



3. There are two pairs of limbs, whicli form packllcs, having the elements 

 arranged in one plane, and incapable of rotation or Hexure on cacli other. 



4. There is no sternum. ' 



5. The scapular arch consists of scapula and coracoid only. 



6. There is no sacrum. 



7. The pelvis consists of slender claments, of which the inferior are 

 nearly transverse, and meet without uniting on the middle line below. 



8. The opisthotic bone projects free from the cranium as tlie suspenso- 

 rium of the quadrate 1)one, and is supported and embraced l)y a pedestal pro- 

 jecting from the cranial walls, composed of the prootic in fnjnt and the exoc- 

 cipital behind. 



9. The stapes lies in a groove on the posterior side of this suspensorium, 

 and is produced to the os quadratum. 



10. There is no quadrato-jugal' arch. 



11. The parietal bone is decurved posteriorly, forming the cranial wall 

 in front of the prootic. 



12. The brain-chaml)er is not ossified in front. 



13. The squamosal bone is present, merely forming the posterior part of 

 the zygomatic arch. 



14. The mandible is composed of all the elements characteristic of rep- 

 tiles: the articular and surangular distinct; the angular represented l)y its 

 anterior portion only ; and the coronoid present. 



15. The atlas consists of a basal and two lateral pieces only ; the odon- 

 toid is distinct, and is bounded by a free hypapo|)hysis, besides the hypapo- 

 physis of the axis. 



16. The caudal vertebrte support chevron-bones. 



17. The teeth possess no true roots. 



The free quadrate bone and simple costal articulations at once refer this 

 order to the Strcptostylicate division of the Repfi/ia, which cml)raccs only the 

 three orders of Lacertilia, Pythonomorpha, and Ophidia. There are several 

 characters, however, in which it resembles some orders of one other i)rimary 

 group, viz, the Synapfosauria, which embraces the Sauropterygin, Testut/i- 

 nata, and Rhynchoccphalia} In the al)sence of sternum, it resembles tortoises 

 and Plesiosaurs, and differs from lizards. It resembles the tortoises in the; 



' See Procecdiugs of tbo Aiiioiican Association for tUo Advaiicuineut of Sciouce, vol. XIX, p. 2;i3, 

 1870. 



