SYSTEMATIC REVISION OF THE SUBORDER. 73 



Table III. — Contrasting the Characters of the Genera of the Poliosaurid« — Continued. 



III. Theropleura. 



1. No well-defined diastemal space : a faint notch between the maxillary and premaxillary, filled with teeth. 



2. A single well-defined canine ; incisor teeth enlarged. 



3. Section of tooth at base quadrate. Other characters not shown. 



4. Neural arch coossified with the centrum in the adult. 



5. No great difference in the length of the bottom line of the centra in different parts of the column ; but "as 



deep as long if measured at the center" (Cope). Posterior lumbars not greatly shortened and without 

 wide face for intercentrum. 



6. Anterior dorsals without wide face on the lower part of the anterior face of the centrum for the inter- 



centrum ; without median keel. 



7. Character not shown. 



8. Spine of the axis not elevated ; broadened at the top. 



9. Limb bones without well-developed articular faces. 



10. Character not shown. 



11. Abdominal scales or scutes absent (?). Not observed. 



12. Tail long. 



13. Elongate slender body, probably from 2 to 2.5 meters in length. 



IV. Ehabrosaurus. 



1. Character not shown. 



2. Character not shown. 



3. Character not shown. 



4. Neural arch coossified with centrum. 



5. Posterior lumbars very much shortened and with wide facets on the lower half of the articular faces of the 



centrum. 



6. No wide intercentral face on the anterior face of the centrum in the anterior dorsals. 



7. Character not shown. 



8. Spine of the axis elevated and strong. 



9. Character not shown. 



10. Character not shown. 



11. Character not shown. 



12. Character not shown. 



13. Small, not exceeding i meter. 



Table IV. — Contrasting the Characters of the Genera of the American Clepsydropid«. 



Clepsydrofina:. 



I. Clepsydrofs. 



*i, Diastemal notch present, but small and filled with teeth of small size. 



2. Canine and incisors enlarged. 



3. Teeth with fore and aft cutting edges ; not crenate in all forms. 



4. Neural arches free in the young ; coossified in the adult. 



5. Vertebras with changing length of the bottom line in different parts of the column (?). 



6. Anterior dorsals with the intercentral face on the anterior face of the centrum and with sharp 



keel. 



7. Spines long, but probably nowhere near so elongate as in the genus Dimetrodon. 



8. Character not shown. 



9. Limb bones with well-developed articular condyles. 



10. Humerus without prominent entepicondyle or ectepicondylar notch. 



11. Abdominal scutes absent. (Not observed.) 



12. Tail very long and slender. 



13. From I to 1.3 meters long. 



*The serial numbers are the same as those used for the genera of the other families so that the forms 

 may be contrasted directly. 



